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Poster Abstract

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P-Mo-1: Three observations on the ARPES data of the cuprate superconductors - what the AF spin fluctuation can do and what it cannot Tao Li1 1Department of physics, Renmin University of China, Beijing, China We discuss the origin of the pseudogap phenomena in the cuprate superconductors from the perspective of the spin-Fermion model. We find that the vanishing of the pseudogap around ($,0) as observed recently in Pr1.3−xLa0.7CexCuO4 is consistent with the AF band folding picture of the pseudogap in the electron-doped cuprates, if we assume a strongly momentum dependent quasi-particle scattering rate on the Fermi surface[1,4]. However, we find that the pseudogap in the hole-doped cuprates is unlikely an AF band folding gap. In particular, we show that electron pairing is indispensable to eliminate the Fermi level crossing along ($,0)-($,$) in a way consistent with the ARPES observation on the underdoped Bi-2201 system around T*[2,4]. Nevertheless, we find that the AF spin fluctuation in the hole-doped cuprates is responsible for the high energy hump structure, the mismatch between the hump back-bending momentum and the bare Fermi momentum, and in particular, the extremely flatness of the anti-nodal quasi-particle dispersion in the superconducting state [3,4]. [1] Hario et al, arXiv: 1801.04147. [2] Hashimoto et al, Nat. Phys. 6, 414 (2010). [3] R.H. He et al, Science 331, 1579 (2011). [4] Tao Li and Da-Wei Yao, arXiv: 1803.08226(EPL,124,47001,2018); arXiv:1805.05530; arXiv:1805.04883.

P-Mo-2: Coexistence of electronic superstructures in high-Tc cuprate Bi2Sr2CaCu2O8+x studied by STM/STS S. Mizuta1, T. Kurosawa1, N. Momono2, H. Yoshida1, M. Oda1 and M. Ido1 1Department of Physics, Hokkaido University, Sapporo 060-0810, Japan 2Department of Applied Sciences, Muroran Inst. of Technology, Muroran 050-8585, Japan We performed STM/STS measurements at 8 K in underdoped Bi2Sr2CaCu2O8+x with a hole doping level of ~0.12, and examined three kinds of electronic superstructures: checkerboard modulation (CBM) [1], unidirectional Cu–O–Cu bond-centered modulation (BCM) [2, 3] and quasiparticle interference modulation (QPIM) [2]. We confirmed that CBM is observed in

spatial maps of the local density of states (LDOS) for energies around DSG, where STS spectra exhibit sub-gap structure. It was also found that the CBM coexists with BCM, whose

characteristic energy is the pseudogap energy DPG, and QPIM hosted by nodal superconducting gap. An interesting feature for these electronic superstructures is that they include characteristic structures with a length scale of four times the lattice constant along the Cu–O–Cu directions. In this conference, we will discuss the spatial phase relation among the characteristic structures in terms of cross-correlation functions between any two of them. [1] C. Howald et al., Phys. Rev. B 67, 014533 (2003). [2] Y. Kohsaka et al., Nature 454, 1072 (2008). [3] M. H. Hamidian et al., Nat. Phys. 12, 150 (2016).

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P-Mo-3: Study of superconducting fluctuation in cuprate superconductors through the observation of Higgs mode oscillation Kota Katsumi1, Zhi Zhong Li2, Hélène Raffy2, Yann Gallais3 and Ryo Shimano1,4

1 Department of Physics, University of Tokyo, Hongo, Tokyo, 113-0033, Japan 2 Laboratoire de Physique des Solides (CNRS UMR 8502), Bâtiment 510, Université Paris-Sud/Université Paris-Saclay, 91405, Orsay, France 3 MPQ CNRS, Université Paris Diderot, Bâtiment Condorcet, 75205 Paris Cedex 13, France 4 Cryogenic Research Center, The University of Tokyo, Tokyo, 113-0032, Japan Superconducting fluctuation (SCF) in cuprates has been extensively studied to reveal the pairing nature above Tc. Various measurements, such as the Nernst signal, heat capacity and ac-conductivity have been provided the signature of the SCF, whereas the onset temperature of the SCF depends on the measurement scheme. Here we focus on the Higgs mode (HM) which directly manifests the presence of spontaneous symmetry breaking, in particular the development of superconducting phase coherence. To this end, we performed a THz pump-optical probe spectroscopy for underdoped and overdoped Bi2Sr2CaCu2O8+δ (Bi2212) thin films. We also measured the THz optical conductivity and extracted the superfluid density (ns) by two-fluid model. The onset temperature of the HM (THM) shows a good agreement with that of ns for both samples. We discuss the doping dependence of THM for Bi2212 single crystals in our previous work [1]. [1] K. Katsumi et al., Phys. Rev. Lett. 120, 117001 (2018).

P-Mo-4: Effect of structural supermodulation on superconductivity in tri-layer cuprate Bi2Sr2Ca2Cu3O10+δ C. Zou1, Z. Hao1, and Y. Wang1 1State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China. We investigate the spatial and doping evolutions of the superconducting properties of tri-layer cuprate Bi2Sr2Ca2Cu3O10+δ by using scanning tunneling microscopy and spectroscopy. Both the superconducting coherence peak and gap size exhibit periodic variations with the structural supermodulation, but the effect is much more pronounced in the underdoped regime than at optimal doping. Moreover, a new type of tunneling spectrum characterized by two distinct superconducting gaps emerges with increasing doping, and the two-gap features are also affected by the supermodulation. We propose that the interaction between the inequivalent outer and inner CuO2 planes is responsible for these novel features that are unique to tri-layer cuprates.

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P-Mo-5: Carrier-doping effects on Tc in the undoped (Ce-free) superconductor T’-La1.8Eu0.2CuO4 T. Sunohara, T. Kawamata, K. Shiosaka, T. Takamatsu, T. Noji, M. Kato, and Y. Koike

Department of Applied Physics, Tohoku University, Sendai, Miyagi 980-8579, Japan Since the discovery of superconductivity in undoped (Ce-free) superconducting thin films of RE2CuO4 (RE = rare earth element) with the Nd2CuO4-type (so-called T’-type) structure [1,2], the mechanism of the superconductivity has attracted great interest. The undoped superconductivity has also been confirmed in the bulk polycrystal of T’-La1.8Eu0.2CuO4 and the superconducting transition temperature, Tc, has been found to decrease by the hole doping in bulk polycrystals of T’-La1.8-xEu0.2MxCuO4 (M = Sr, Ca) [3,4]. To investigate the electron-doping effect, we have synthesized bulk polycrystals of T’-La1.8Eu0.2CuO4-yFy (y = 0 - 0.15) by the fluorination of T’-La1.8Eu0.2CuO4 using NH4F. From the magnetic susceptibility measurements, Tc has been found to increase with increasing y, exhibit the maximum value of ~ 23K at y = 0.025 and decrease. Such a dome-like dependence of Tc on the carrier concentration is explained in terms of the pairing mediated by spin fluctuations based on the d-p model calculation [5].

[1] O. Matsumoto et al., Physica C 469, 924 (2009). [2] O. Matsumoto et al., Phys. Rev. B 79, 100508(R) (2009). [3] T. Takamatsu et al., Appl. Phys. Express 5, 073101 (2012). [4] T. Takamatsu et al., Phys. Procedia 58, 46 (2014). [5] K. Yamazaki et al., J. Phys: Conf. Ser. 871, 012009 (2017).

P-Mo-6: Reduction annealing effects on charge and spin excitations in Nd2-xCexCuO4 studied by resonant inelastic x-ray scattering K. Ishii1, S. Asano2, M. Ashida3, M. Fujita2, J. Mizuki3, B. Yu4, M. Greven4, J. Okamoto5, A. Singh5, D. J. Huang5 1Synchrotron Radiation Research Center, National Institutes for Quantum and Radiological Science and Technology, Sayo, Hyogo 679-5148, Japan 2Tohoku University, Sendai 980-8577, Japan 3Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan 4University of Minnesota, Minneapolis, Minnesota 55455, USA 5National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan In the electron-doped cuprates RE2-xCexCuO4 (RE: trivalent rare earth), post-annealing of the crystals under reduction atmosphere is necessary for the occurrence of the superconductivity in addition to the electron doping by substituting of Ce for RE. Recently, an improved annealing procedure expanded the superconducting phase to lower Ce concentration than before, and superconductivity was observed even without Ce substitution (x = 0) in thin films and polycrystalline samples [1]. These results necessitate a systematic reexamination of the effects of reduction annealing. We performed resonant inelastic x-ray scattering at the Cu K- and L3-edges focusing on the effects on charge and spin excitations in the electron-doped cuprates Nd2-xCexCuO4. [1] Reviewed in T. Adachi et al., Condens. Matter 2, 23 (2017).

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P-Mo-7: Observation of Band Dispersion of Cuprate Superconductor by Laser-excited Angle Resolved Photoemission Spectroscopy Y. Takeuchi1, K. Yamagami1, K. Sorime1, H. Kondo1, H. Yomosa1, S. Ikeda1, H. Fujiwara1, H. Eisaki2, A. Sekiyama1, T. Kiss1

1Department of Engineering Science, Osaka Univ., Toyonaka, Osaka 560-8531, Japan 2National Institute of Advanced Industrial Science and Technology(AIST), Tsukuba, Ibaraki 305-8560 Japan Angle resolved photoemission spectroscopy (ARPES) is a powerful tool to observe electronic structures, and revealed many anomalous properties such as superconductivity. Recently, laser-excited photoemission spectroscopy (Laser-PES) plays important roles to study the detailed electronic structure near the Fermi level in the high-Tc cuprates [1, 2]. In the high-Tc cuprates, the competition between antiferromagnetism and superconductivity is seen in multi-layer systems[3]. We have developed 6 eV Laser-ARPES system to reveal the detailed electronic structures. To

confirm the performance of the system and observe the small gap structure of well-known Bi2Sr2CaCu2O8+δ (Bi2212) around nodal point, we have performed a 6 eV Laser-ARPES measurements. In this presentation, we will report the results. [1] T. Kiss et al., Rev. Sci. Instrum. 79, 023106 (2008). [2] S. Kunisada et al., Phys. Rev. Lett. 119, 217001 (2017). [3] S. Shimizu et al., Phys. Rev. B 85, 024528 (2012)

P-Mo-8: Photoexcited dynamics of superconductivity in La2−xSrxCuO4 probed by Josephson plasma resonance H. Niwa1, N. Yoshikawa1, D. Song2, H. Eisaki2 and R. Shimano1,3 1Department of Physics, The University of Tokyo, Hongo, Tokyo 113-0033, Japan 2National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8568, Japan 3Cryogenic Research Center, The University of Tokyo, Yayoi, Tokyo 113-0032, Japan We report the photoexcited nonequilibrium dynamics of a single-layer cuprate superconductor, La2−xSrxCuO4, observed by near-infrared optical pump and terahertz (THz) probe spectroscopy. At below the critical temperature Tc, the photoexcitation leads to the redshift of the Josephson plasma resonance that sustains for several hundreds of picoseconds after the photoexcitation. We show that the spectral behavior in the quasi-equilibrium state after the photoexcitation is described by the pump-induced surface heating which causes the destruction of superconductivity. We also discuss the validity of the analysis method which has been conventionally used to obtain the transient spectra in optical pump and terahertz probe experiments with the penetration-depth mismatch. [1] H. Niwa, N. Yoshikawa, K. Tomari, R. Matsunaga, D. Song, H. Eisaki and R. Shimano, “Light-induced nonequilibrium response of the superconducting cuprate La2−xSrxCuO4” arXiv:1904.07449 (2019).

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P-Mo-9: Electron Mass Enhancement near a Nematic Quantum Critical Point in NaFe1−xCoxAs Rui Zhou1 and Guo-qing Zheng1,2 1Institute of Physics, Chinese Academy of Sciences, and Beijing National Laboratory for Condensed Matter Physics,Beijing 100190, China 2Department of Physics, Okayama University, Okayama 700-8530, Japan A magnetic order can be completely suppressed at zero temperature (T), by doping carriers or applying pressure, at a quantum critical point, around which physical properties change drastically. However, the situation is unclear for an electronic nematic order that breaks rotation symmetry. In this talk, we will show nuclear magnetic resonance studies on NaFe1−xCoxAs where magnetic and nematic transitions are well separated. We discovered two peaks in the doping dependence of λ2

L(T∼0), one at xM ~ 0.027 where the spin-lattice relaxation rate shows quantum critical behavior, and another at xc ~ 0.032 around which the nematic transition temperature extrapolates to zero and the electrical resistivity shows a T-linear variation. Our results indicate that a nematic quantum critical point lies beneath the superconducting dome at xc where m* is enhanced. The impact of the nematic fluctuations on superconductivity will also be discussed. [1] C. G. Wang, Z. Li, J. Yang, L. Y. Xing, G. Y. Dai, X. C. Wang, C. Q. Jin, R. Zhou, and Guo-qing Zheng, Phys. Rev. Lett. 121, 167004 (2018).

P-Mo-10: Shot noise as a probe for the pairing symmetry of Iron pnictide superconductors Colin Benjamin and Tusaradri Mohapatra National Institute of Science Education and Research, Odisha, India One of the outstanding problems in Iron pnictide research is the unambiguous detection of its pairing symmetry. The most probable candidates are the two-band s++ and sign reversed s± wave pairing. In this work the Andreev conductance and shot noise are used as a probe for the pairing symmetry of Iron pnictide superconductors. Clear differences emerge in both the zero bias differential conductance and the shot noise in the tunneling limit for the two cases enabling an effective distinction between the two. Our work is significant because this is for the first time that shot noise has been used to detect pairing symmetry of any superconductor let alone an Iron based superconductor. We show that regardless of whether we use normal metal or ferromagnet, the differential shot noise in the tunnel barrier z→∞ limit vanishes for s± pairing, while it is finite for s++ pairing for strong coupling between the two bands. [1] C. Benjamin and T. Mohapatra, arXiv:1904.00201 (2019).

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P-Mo-11: Nematic fluctuation and resonance in iron pnictide BaFe2(As,P)2 S. Miyasaka1, T. Adachi1, M. Nakajima1, and S. Tajima1 1Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan Various iron-based superconductors show electronic nematicity. Its origin and relationship with the superconductivity (SC) have been intensively debated, but they still remain unclear. Raman scattering spectroscopy is a powerful tool to investigate the electronic properties in solid. In particular, its symmetry-resolved feature enables us to directly access the bare electronic nematicity. In this work, we have investigated the nematic Raman response in BaFe2(As,P)2. The nematic susceptibility has been estimated from the quasi-elastic peak of B1g Raman scattering spectra, and its temperature (T) dependence can be fitted by the Curie-Weiss law. The nematic fluctuation temperature T* is determined as the starting T of the enhancement of the nematic susceptibility. T* is higher than the SDW transition temperature Ts and decreases with increasing P doping level. The bare nematic transition temperature T0 (<Ts) determined by the fitting of Curie-Weiss law also decreases with P doping and becomes 0 K near the magnetic/structural quantum critical point (QCP). This behavior indicates that the nematic QCP exists near magnetic/structural QCP and near optimally doping region for SC in the phase diagram of BaFe2(As,P)2. In the optimally doping region, not only the pair breaking peak but also the nematic resonance one with large intensity appear below Tc in Raman scattering spectra with B1g symmetry. The energy of the nematic resonance peak is slightly lower than the pair breaking peak energy. The existence of clear nematic resonance peak suggests the remarkable correlation between SC and nematic fluctuation.

P-Mo-12: Detailed study of temperature dependence of spin fluctuations in FeSe0.5Te0.5 K. Ikeuchi1, K. Kodama2, M. Ishikado1, M. Nakamura3, R. Kajimoto3, and S. Shamoto4 1Neutron Science and Technology Center, CROSS, Tokai, 319-1106, Japan 2Materials Sciences Research Center, JAEA, Tokai, Ibaraki 319-1195, Japan 3J-PARC Center, JAEA, Tokai, Ibaraki 319-1195, Japan 4Advanced Science Research Center, JAEA, Tokai, Ibaraki 319-1195, Japan

Nematic behavior of electronic properties has been found in iron-based superconductors. In order to elucidate the characteristics, we have reinvestigated magnetic excitation of FeSe0.5Te0.5 using inelastic neutron scattering by the Fermi chopper spectrometer. Here, the detailed temperature dependence of the magnetic excitation will be reported. The characteristic changes with decreasing temperature from room temperature to superconducting state are as follows; 1) the split incommensurate peaks at low energy gradually become merged, as reported by Xu et al.[1]: 2) the collective excitation at the top energy of its dispersion loses the intensity gradually. The evolution of the commensurate structure can be a key aspect as a critical behavior of the nematicity in relation to the appearance of the superconductivity. [1] Z. Xu, J. Wen, Y. Zhao, M. Matsuda, W. Ku, X. Liu, G. Gu, D.-H. Lee, R. J. Birgeneau, J. M. Tranquada, G. Xu, Phys. Rev. Lett. 109 (2012) 227002.

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P-Mo-13: Novel electronic nematicity in the heavily hole-doped iron pnictides K. Ishida1, M. Tsujii1, Y. Mizukami1, S. Ishida2, A. Iyo2, H. Eisaki2, K. Grube3, T. Wolf3, Hilbert. v. Lӧhneysen3, R. M. Fernandes4, and T. Shibauchi1

1Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan 2Electronics and Photonics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan 3Institut für Festkőrperphysik, Karlsruher Institut für Technologie, 76021 Karlsruhe,�Germany 4School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, U.S.A. Electronic nematicity, which breaks rotational symmetry of the underlying lattice, is a key feature in the iron-based superconductors. However, the directors of these nematic domains has been considered to be confined to Fe-Fe directions of the tetragonal lattice, which was described as B2g Ising-nematic state. Here we report the systematic elastoresistance measurements in Ba1-xRbxFe2As2 and CsFe2As2, which allow us to evaluate the nematic fluctuations. In RbFe2As2 and CsFe2As2, we find that B1g nematic fluctuations, whose director is rotated 45 degree from that of the usual B2g nematicity, become dominant compared with B2g nematic fluctuations. Furthermore, for the intermediate doping between these two distinct nematic phase, B1g and B2g nematic fluctuations exhibit identical Curie-Weiss behaviors, revealing that nearly XY-nematic fluctuation regime.

P-Mo-14: Development of orbital fluctuations and s-wave superconductivity due to AL-VC in electron-doped FeSe Y. Yamakawa1, S. Onari1, and H. Kontani1 1Department of Physics, Nagoya University, Nagoya, Aichi 464-8602, Japan High-Tc superconducting state in heavily electron-doped FeSe is one of the key unsolved problems in Fe-based superconductors. We analyze the electronic states by including higher-order many-body effects, not only the vertex corrections (VCs) [1] but also the self-energy effect. Among VCs, the Aslamazov-Larkin term (AL-VC) is important since the nematic fluctuations originate from the strong orbital-spin mode coupling described by the AL-VC. The multi-orbital Hubbard model is constructed by using the first-principles calculation for (Li,Fe)OHFeSe, which is one of the bulk electron-doped FeSe systems. The virtual crystal approximation (VCA) is employed to take the doping effect into account on the band structures seriously. We find that both the orbital and spin fluctuations increase with electron doping, since the bandwidth decreases by electron doping in the VCA. In addition, we solve the linearized gap equation including the VCs and self-energy, and explain the high-Tc fully-gapped s-wave state in electron-doped FeSe. It originates from the strong attractive intra- and inter-pocket interactions due to orbital fluctuations driven by the AL-VC. In the rigid band model, in contrast, both fluctuations decrease monotonically with electron-doping, and therefore the high-Tc state cannot be explained. [1] Y. Yamakawa and H. Kontani, Phys. Rev. B 96, 045130 (2017).

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P-Mo-15: Effect of electron correlations on spin excitation bandwidth in Ba0.75K0.25Fe2As2 as seen via time-of-flight inelastic neutron scattering N. Murai1, K. Suzuki2, S. Ideta3, M Nakajima4, K. Tanaka3, H. Ikeda5, and R. Kajimoto1

1Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan

2Research Organization of Science and Technology, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan 3UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan 4Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan 5Department of Physics, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan We use inelastic neutron scattering (INS) to investigate the effect of electron correlations on spin dynamics in the iron-based superconductor Ba0.75K0.25Fe2As2. Our INS data show a spin-wave-like dispersive feature, with a zone boundary energy of 200 meV. By combining angle-resolved photoemission spectroscopy (ARPES) measurements and first-principles calculations, we show that the measured spin excitations are heavily renormalized due to the correlated Fe-3d bands with enhanced effective electron masses. These results highlight the strongly correlated nature of iron-based superconductors that should be considered for a realistic treatment of the spin dynamics.

P-Mo-16: Strain induced coexistence of unidirectional charge modulations and superconductivity in LiFeAs C. Trainer1, C. M. Yim1 and P. Wahl1

1SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife, KY16 9SS, UK Symmetry breaking "nematic" electronic states are ubiquitous among the Iron based superconductors and their relevance to the Cooper pairing mechanism responsible for the superconductivity as well as for the structural and magnetic transitions that many also undergo is believed to hold important clues to understand the unconventional superconductivity. Among the iron-based superconductors, LiFeAs stands out in being a stoichiometric material that does not show any trace of nematic order[1] or magnetic order[2] and remains tetragonal even down to the lowest temperatures where it exhibits a C4 symmetric superconducting state [1]. We have conducted a low temperature STM study of LiFeAs subject to a uniaxial strain, thus changing the crystal symmetry from tetragonal to orthorhombic. In this talk I will outline and discuss our results in which we not only detect a strong effect of strain on the atomic-scale strength of the superconducting pairing but also a strain-induced charge modulation that competes with superconductivity and dramatically lowers the symmetry of the electronic states [3]. [1] M.P. Allan et al., Science 336, 563 (2012). [2] N. Qureshi et al., Phys. Rev. Lett. 108, 117001 (2012). [3] C.M. Yim & C. Trainer et al., Nature Communications 9, 2602 (2018).

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P-Mo-17: Effect of electron doping in FeTe0.65Se0.35 realized by Co and Ni substitution P. Starowicz1, M. Rosmus1, R. Kurleto1, D. J. Gawryluk2,3, J. Goraus4, M. Z. Cieplak3 1M. Smoluchowski Institute of Physics, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland 2Laboratory for Multiscale Materials Experiments, Paul Scherrer Institut, 5232 Viligen PSI, Switzerland 3Institute of Physics, Polish Academy of Sciences, Lotników 32/46, 02-668 Warszawa, Poland 4Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland Angle-resolved photoemission spectroscopy reveals effects of electron doping, which appear in Co and Ni substituted FeTe0.65Se0.35. These are band shifts, expansion of electron pockets and reduction of hole pockets with a Lifshitz transition. The results explain qualitatively a peculiar behavior of Hall coefficient. Fermi surface volume and band shifts indicate that Co doping assures more efficient transfer of electrons to valence band as compared to the effect of Ni substitution. Data analysis reveals the evidence of some non-rigid band shifts. Electron pockets have different shape in case of Co and Ni substitution. Moreover, the hole band exhibits parabolic dispersion when it is below the Fermi energy but its effective mass is strongly reduced, if it participates in Fermi surface. Fermi surface of superconducting Fe1.01Te0.67Se0.33 shows rather imperfect nesting between hole and electron pockets. Co and Ni substitution, which reduces critical temperature, causes also a further deviation from nesting properties.

P-Mo-18: Atomic-scale visualization of superfluid in the iron-based superconductor FeTe0.55Se0.45 Doohee Cho1, Koen M. Bastiaans1, Damianos Chatzopoulos1, Genda Gu2, Milan P. Allan1 1 Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands 2 Condensed Matter Physics & Materials Science Department, Brookhaven National Laboratory, Upton, NY 11973, USA The inhomogeneous superfluid density is one of the long-standing mysteries in unconventional, strongly correlated superconductors. We use atomic-resolution Josephson scanning tunneling microscopy (STM) to visualize the spatial variations of the superfluid in the iron-based superconductor FeTe0.55Se0.45 [1]. By simultaneously acquiring the topographic and electronic properties, we find that this inhomogeneity in the superfluid is not caused by structural disorder or strong inter-pocket scattering, and does not correlate with variations in the energy of the Cooper pair-breaking gap. Instead, we see a clear spatial correlation between superfluid density and the quasiparticle strength, defined as the height of the coherence peak, on a local scale. [1] Cho, D., et al. "A strongly inhomogeneous superfluid in an iron-based superconductor." arXiv:1901.00149 (2019).

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P-Mo-19: High-Resolution ARPES Study of Bi2Te3/FeTe heterostructure K. Owada1, K. Nakayama1, R. Tsubono1, K. Shigekawa1, G. Phan1, K. Sugawara1,2,3, T. Takahashi1,2,3, and T. Sato1,3 1Department of Physics, Tohoku University, Sendai 980-8578, Japan 2WPI-AIMR, Tohoku University, Sendai 980-8577, Japan 3CSRN, Tohoku University, Sendai 980-8577, Japan Recent discovery of interfacial superconductivity with Tc = 12 K in a hybrid of topological insulator Bi2Te3 and iron chalcogenide FeTe (Bi2Te3/FeTe) [1] triggered intensive debates on the origin of superconductivity because parent Bi2Te3 and FeTe are both non-superconducting. This new interfacial superconductor is also attracting particular attention as a topological superconductor candidate because a coupling of topological surface states and superconductivity via a proximity effect would lead to topological superconductivity hosting Majorana fermions that are useful for a fault-tolerant quantum computation. In this study, we have performed angle-resolved photoemission spectroscopy (ARPES) measurements of Bi2Te3/FeTe grown by molecular-beam-epitaxy technique. We observed Dirac-cone topological surface states of Bi2Te3 and several renormalized Fe-3d bands of FeTe, and their energy shifts due to a charge transfer at the interface. We discuss the implications of our results in relation to the origin of interfacial superconductivity and the possible realization of topological superconductivity. [1] Q. L. He et al., Nature Commun. 5, 4247 (2014).

P-Mo-20: Majorana braiding dynamics in class D topological superconductor T. Sanno, T. Mizushima, A. Tsuruta, and S. Fujimoto Department of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan A Majorana fermion is a self-hermite fermion; i.e. particle and anti-particle are equated. Quasiparticles showing this property appear in condensed matter physics. Majorana quasiparticles are realized as zero energy bound states in vortex cores of topological superconductors, which are called Majorana zero modes. They are robust against disturbance due to their non-local character. Quantum computation using Majorana zero modes is currently attracting much attention[1][2]. In this presentation, we discuss about quantum dynamics of the exchange of positions of Majorana zero modes, which is called braiding and utilized for the construction of decoherence-free quantum computation, in a two-dimensional topological superconductor. We demonstrate the acquisition of the geometric phase, fermion parity conservation after braiding Majorana fermions and non-abelian statistics by numerically solving the TDBdG equation [3][4]. Fermion parity, which plays the role of qubit, is conserved during braiding. Also, we analytically found that direct transition between particle-hole pair partners is forbidden by particle-hole symmetry in class D topological superconductor. [1] D. A. Ivanov: Phys. Rev. Lett. 86, 268 (2001) [2] C. Nayak, S. Simon, M. Freedman, S. Das Sarma: Rev. Mod. Phys. 80, 1083 (2008) [3] L. Fu and C L Kane: Phys. Rev. Lett. 100, 096407 (2008) [4] H. Tal-Ezer and R. Kosloff: J. Chem. Phys. 81, 3967 (1984)

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P-Mo-21: Laser-induced topological phase transitions in bilayer transition metal dichalcogenide H. Chono1, K. Takasan2, and Y. Youichi1

�1Department of Physics, Kyoto University, Kyoto 606-8502, Japan 2Department of Physics, University of California, Berkeley, California 94720 USA

Application of laser light can be a powerful tool for changing and controlling properties of materials. In recent years, topological phases in periodically driven systems by laser light have been actively investigated. For example, photoinduced quantum anomalous Hall states were theoretically proposed in laser-irradiated graphene [1] and the observation of this phenomenon was experimentally reported very recently [2]. It was also proposed that topological superconductivity can be induced with laser light in cuprate thin films [3]. Motivated by these situations, we theoretically investigate the laser-induced topological phase transitions in 2Hb structure of bilayer transition metal dichalcogenides (TMDs). Analyzing the tight-binding model for laser-irradiated bilayer TMDs with use of the Floquet theory, we show a topological phase transition in the band structure and the laser-induced topological superconductivity.

[1] T. Oka et al., Phys. Rev. B 79, 081406 (2009). [2] J. W. Mclver et al., arXiv: 1811.03522 [3] K. Takasan et al., Phys. Rev. B 95, 134508 (2017).

P-Mo-22: Research on Unconventional Pairing Mechanism at Superconducting LaAlO3/SrTiO3 Interface J. C. Nie Department of Physics, Beijing Normal University, Beijing 100875, China LaAlO3/SrTiO3(LAO/STO) oxide heterostructure interfaces were prepared by LMBE. The two-dimensional superconductivity of the LAO/STO(110) interface was confirmed with critical temperature Tc of about 200mK [1]. The experimental results [2] show that with the decrease of the back-gate-voltage VG, Tc forms a dome-shaped superconducting region, while the upper critical field Hc2 monotonically increases. This unconventional trend indicates that the Cooper pair potential is stronger in underdoped region, which is analogous to that of pseudogap in high-Tc cuprates. Besides, possible coexistence of superconductivity and ferromagnetism was observed at the LAO/STO interface: magnetoresistance peaks were found near the zero magnetic field [3]. The relevant phase sensitivity experiments were carried out. [1] Y. L. Han, et al. Appl. Phys. Lett., 105, 192603 (2014). [2] S. C. Shen, et al. Sci.. Rep., 6, 28379 (2016). [3] S. C. Shen, et al. Phys. Rev. B, 94, 144517 (2016).

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P-Mo23: Near surface properties of the magnetic field distribution of the type-I superconductor indium V. Kozhenikov1, A. Suter2, T. Prokscha2, and C. Van Haesendonck3 1Tulsa Community College, Tulsa, Oklahoma 74119, USA 2Paul Scherrer Institut, 5232 Villigen PSI, Switzerland 3Solid State Physics and Magnetism Section, KU Leuven, BE-3001 Leuven, Belgium We report on direct measurements of the field distribution and shape of domains across the surface of high-purity type-I (indium) films in perpendicular field geometry using Low-Energy muon Spin Rotation spectroscopy (LE-µSR). We find that at low applied fields the field distribution and domains’ shape agrees with that proposed by Tinkham, contradicting Landau’s original work. However, for high fields our data suggest that reality differs from theoretical expectations. In particular, the width of the superconducting laminae can expand near the surface leading to formation of a maximum in the static magnetic field in the current-free space outside the sample. We speculate that the apparent contradiction of our observations with classical electrodynamics is due to the inapplicability of the standard boundary conditions to the vicinity of an “active” superconductor.

P-Mo-24: Two competing superconducting phases and electron-hole doping asymmetry in k-type molecular conductors Hiroshi Watanabe1, Hitoshi Seo1,2, and Seiji Yunoki1,2,3 1RIKEN Cluster for Pioneering Research (CPR), Wako 351-0198, Japan 2RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan 3RIKEN Center for Computational Science (R-CCS), Kobe 650-0047, Japan Unconventional superconductivity (SC) in molecular conductors is observed at the border of metal-insulator transitions under the influence of geometrical frustration [1]. The symmetry and the mechanism of SC are highly controversial. In this study, we investigate the extended

Hubbard model for k-(ET)2X using the variational Monte Carlo method [2,3]. We find significant electron-hole doping asymmetry in the ground-state phase diagram where AF spin order, several patterns of charge order, and SC compete with each other. Hole-doping stabilizes the AF phase and promotes SC with “dxy”-wave symmetry, which has similarities with high-Tc cuprates. On the other hand, in the electron-doped side, geometrical frustration destabilizes the AF phase and the enhanced charge correlation induces novel SC with “extended-s+dx2

-y2”-wave symmetry. The electron-hole doping asymmetry is attributed to the degree of frustration that is controlled by carrier doping. Our results provide a novel understanding of how physics of molecular conductors and high-Tc cuprates are distinct. [1] K. Kanoda, J. Phys. Soc. Jpn. 75, 051007 (2006). [2] HW, H. Seo, and S. Yunoki, J. Phys. Soc. Jpn. 86, 033703 (2017). [3] HW, H. Seo, and S. Yunoki, arXiv:1811.09035.

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P-Mo-25: Effect of carrier doping on the pairing competition in organic conductors κ-(BEDT-TTF)2X H. Aizawa1 and H. Seo2,3

1Institute of Physics, Kanagawa University, Yokohama, Kanagawa 221-8686, Japan 2Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan 3Center for Emergent Matter Science (CEMS), RIKEN, Wako, Saitama 351-0198, Japan

The family of quasi-two-dimensional organic conductors κ-(BEDT-TTF)2X shows intriguing phenomena owing to strong electron correlation, such as Mott transition, quantum spin liquid behavior, and anisotropic superconductivity. Recently, carrier doping to these organic salts have become possible [1], thus a new approach is obtained to reveal the physics of electron correlation, and connections to high-Tc cuprates are discussed [2]. Here we theoretically study the effect of the carrier doping on the pairing competition between the “extended-s + dx2

–y2”-wave and dxy-wave superconductivity, based on the four band Hubbard model within two-particle self-consistent approximation. The results show a significant electron-hole asymmetry, namely, the enhancement of “extended-s + dx2

–y2”-(dxy)-wave pairing in the electron-(hole-)doping side. [1] Y. Kawasugi et al., Nat. Commun. 7, 12356 (2016); H. Oike et al., Nat. Commun. 8, 756 (2017). [2] H. Watanabe, H. Seo, and S. Yunoki, J. Phys. Soc. Jpn. 86, 033703 (2017); preprint (arXiv:1811.09035)

P-Mo-26: Observation of Mott state melting in Nb doped 1T-TaS2 S. Ohta1, S. Moroi1, A. Nomura1, Y. Fujisawa2, and H. Sakata1 1 Department of physics, Tokyo University of Science, Shinjyuku-ku, Tokyo 162-8601, Japan 2 Okinawa Institution of Science and Technology, Onna-son Kunigami-gun Okinawa 904-0495, Japan Transition metal dichalcogenide 1T-TaS2 has a unique feature such as the emergence of the Mott state in the commensurate CDW (CCDW) state below 190 K. This Mott state melts with substitution of Ta for small amount of Fe about a few percent, and superconductivity appears

[1]. Furthermore, the Mott melting state was found to show domain structure by scanning

tunneling microscopy and spectroscopy (STM/STS) measurements [2]. To clarify the reason for the formation of the CDW domain structure and the suppression of the Mott state by the transition metal substitution in 1T-TaS2, we performed STM/STS measurements on the samples doped with Nb, which has the same valence as that of Ta while ionic radius is slightly different, to compare the results with those in Fe doped samples. It was found that the CDW domain structure was also formed in Nb doped 1T-TaS2 and the Mott state melted. However, the effect of Nb doping was far weaker than that of Fe doping. [1] L. J. Li et al., EPL 97 67005 (2012). [2] Y. Fujisawa et al., J. Phys. Soc. Jpn. 86, 113703 (2017).

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P-Mo-27: Multiorbital Ferroelectric Superconductivity in SrTiO3 S. Kanasugi and Y. Yanase Department of Physics, Kyoto University, Kyoto 606-8502, Japan SrTiO3 (STO) is a unique example of a system which exhibits both quantum paraelectricity and superconductivity. Thus, it is expected that the superconducting state is closely related to the intrinsic ferroelectric (FE) instability. Indeed, recent experiments suggest the existence of a coexistent phase of superconductivity and ferroelectricity in Sr1-xCaxTiO3-y [1]. In this presentation, we will discuss that STO can be a platform of the FE superconductivity which is characterized by a FE transition in the superconducting state [2]. By analyzing a multiorbital model for t2g electrons, we investigate the stability of the FE superconductivity. It is shown that the FE superconductivity is realized through two different mechanism which relies on the intrinsic spin-orbit coupling. First, the FE superconducting state is stabilized by the Lifshitz transition in dilute carrier density regimes [3]. Second, the FE superconducting state is stabilized under a magnetic field. In addition, the importance of the multiband and multiorbital nature of STO for the FE superconductivity is clarified. Then, we predict a topological Weyl superconducting state in the FE superconducting phase of STO. [1] C. W. Rischau et al., Nat. Phys. 13, 643 (2017).

[2] S. Kanasugi and Y. Yanase, Phys. Rev. B 98, 024521 (2018).

[3] E. Cappelluti, C. Grimaldi, and F. Marsiglio, Phys. Rev. Lett. 98, 167002 (2007).

P-Mo-28: Optical Study on Metal-Insulator Transitions of Ni-doping Mott Insulator BaCoS2 Z.Y. Liao1,2, Z.W. Hu1,2, Z.Y. Qiu1,2, C.H. Li1, X.G. Qiu1,2

1Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China The layered transition-metal sulfide system BaCo1-xNixS2-y has received extensive attention due to its transport and magnetic properties resembling those of cuprate superconductors in their normal state[1]. Recently we have succeeded in growing high quality single crystals of BaCo1-xNixS2-y. We have performed an in-plane temperature-dependent infrared spectroscopy on BaCo1-xNixS2-y. Upon warming, we found a metal-insulator transition at about 200 K. In the metallic phase below 200 K, a narrow far-infrared Drude component is present. With increasing temperature across the transition, a clear redistribution of spectral weight is observed, indicating a correlation effect in this material. The study of metal- insulator transition may contribute to the understanding of various normal state properties of the cuprate superconductors. [1] J. Takeda, K. Kodama, H. Harashina, and M. Sato, J. Phys.Soc.Jpn. 63, 3564(1994).

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P-Mo-29: Spectroscopy of Ag-Bi-O Phases Synthesized Under High Pressure M. Oudah,a, b M. Kim,a G. McNally,a K. Rabinovich,a S. Borris,a D. Bonn,b B. Keimer,a and H. Takagi,a, c a Max Planck Institute for Solid State Research, Stuttgart, Germany b Stewart Blusson Quantum Matter Institute, University of British Columbia, Canada c Department of Physics, University of Tokyo, Japan

The stoichiometric silver bismuthate Ag2BiO3 typically contains equal amounts of bismuth in the Bi+3 and Bi+5 states, and this charge ordering renders Ag2BiO3 insulating [1]. Recent theoretical predictions of metal-insulator transition and Weyl semimetal state in Ag2BiO3 have revived the interest in this material [2]. However, such novel properties are only expected in the absence of the charge ordering of bismuth. Here, we utilize spectroscopic tools to examine the possibility of suppressing the charge ordering in Ag2BiO3 via chemical substitution/doping, and achieving topologically nontrivial phase predicted. We present a new high-pressure synthesis route for Ag2BiO3, which we utilize for substituting/doping at the Ag site. Also, we explore the possibility of making Ag-deficient Ag2-xBiO3 phases using high pressure synthesis.

[1] C. B. M. Oberndorfer et al., Solid State Sci. 8, 267 (2006). [2] J. He et al., Nat. Commun. 9, 492 (2018).

P-Mo-30: Relativistic Mott insulator and superconductivity in layered iridates T. Shirakawa1, H. Watanabe1, K. Nishiguchi2, B.-H. Kim3, T. Sato4, and S. Yunoki1 1RIKEN, Saitama 351-0198, Japan, 2Kobe University, Kobe 657-8501, Japan, 3KIAS, Seoul 02455, South Korea, 4Universität Würzburg, 97074, Würzburg, Germany

Based on the three-orbital Hubbard model with a spin-orbit coupling, we have theoretically studied possible superconductivity in a carrier-doped relativistic Mott insulator such as Sr2IrO4 and Ba2IrO4 [1,2]. Applying various numerical methods, we have first established the ground state phase diagram with the t2g

5 electron configuration, which includes a novel spin-orbit induced relativistic jeff=1/2 Mott insulating phase [3-5]. By introducing mobile carriers, we found that d-wave singlet superconductivity is favored in electron doping for the realistic parameter region. Instead, the small spin-orbit coupling and the large Hund’s coupling favor an inter-band s±-wave singlet pairing in the hole-doped region. We also discuss other related systems on the honeycomb lattice structure [6,7] as well as with different electron filling [8]. [1] H. Watanabe, T. Shirakawa, and S. Yunoki, Phys. Rev. Lett. 110, 027002 (2013). [2] K. Nishiguchi, T. Shirakawa, H. Watanabe, R. Arita, and S. Yunoki, arXiv:1904.0181. [3] H. Watanabe, T. Shirakawa, and S. Yunoki, Phys. Rev. Lett. 105, 216410 (2010). [4] H. Watanabe, T. Shirakawa, and S. Yunoki, Phys. Rev. B 89, 165115 (2014). [5] T. Sato, T. Shirakawa, and S. Yunoki, Phys. Rev. B 91, 125122 (2015). [6] B.-H. Kim, T. Shirakawa, and S. Yunoki, Phys. Rev. Lett. 117, 187201 (2016). [7] B.-H. Kim, K. Seki, T. Shirakawa, and S. Yunoki, Phys. Rev. B 99, 155135 (2019). [8] T. Sato, T. Shirakawa, and S. Yunoki, Phys. Rev. B 99, 075117 (2019).

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P-Mo-31: Majorana fermions in strongly correlated system with coexisting superconductivity and noncollinear spin ordering A.O. Zlotnikov Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk 660036, Russian Federation At present, a new mechanism of the formation of the Majorana edge states in topological spin-singlet superconductors due to the presence of the long-range magnetic order is often considered [1-3]. We show a formation of the coexistence state of chiral d+id superconductivity and noncollinear 120-degree spin ordering in the strongly correlated Mott-Hubbard system with a triangular lattice (such as NaxCoO2). There exist different topologically nontrivial phases characterized by the invariant N3 in the coexistence state. The topological transitions between such phases occur upon increasing electron doping. By solving the system of equations for the Green functions the appearance of Majorana fermions in the coexistence phase is shown. With strong correlation effects the Majorana fermion can be defined as the specific superposition of electron-like and hole-like Hubbard fermions. This study was funded by the Russian Foundation for Basic Research (No. 19-02-00348-а) and the Grant of the President of the Russian Federation MK-3594.2018.2. [1] I. Martin, A.F. Morpurgo, Phys. Rev. B 85, 144505 (2012). [2] Y.-M. Lu, Z. Wang, Phys. Rev. Lett. 110, 096403 (2013). [3] V.V. Val’kov, A.O. Zlotnikov, M.S. Shustin, JMMM 459, 112 (2018).

P-Mo-32: Gauge-invariant microscopic kinetic theory of superconductivity in response to electromagnetic fields I: Application to linear response Mingwei Wu University of Science and Technology of China Within a gauge-invariant microscopic kinetic theory, we study the electromagnetic response in the superconducting states. Both superfluid and normal-fluid dynamics are involved. We predict that the normal fluid is present only when the excited superconducting velocity is larger than a threshold. Interestingly, with the normal fluid, we find that there exists friction between the normal-fluid and superfluid currents. Due to this friction, part of the superfluid becomes viscous. Therefore a three-fluid model, normal fluid and nonviscous and viscous superfluids, is proposed to capture both the magnetic and optical responses. Moreover, an exotic phase in which both the resistivity and superconducting gap are finite is predicted.

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P-Mo-33: Seebeck and Nernst effects in a doped spin liquid candidate K. Wakamatsu1, T. Fujii2, Y. Suzuki1, K. Miyagawa1, H. Taniguchi3, and K. Kanoda1

1Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan 2Cryogenic Research Center, University of Tokyo,�Yayoi, Tokyo 113-0032, Japan 3Department of Physics, Saitama University, Saitama, Saitama 338-8570, Japan

κ-(ET)4Hg2.89Br8 is a quasi-two-dimensional organic conductor that possibly host a doped spin liquid [1]. The previous studies revealed a pressure-induced crossover or transition from a non-Fermi liquid (NFL) to a Fermi liquid (FL) in resistivity behavior and from a low to high carrier-density states in the Hall coefficient [2]. The superconductivity that emerges at low temperatures was suggested to exhibit a crossover from local to extended paring with increasing pressure by the evaluation of the coherence length [3]. These results imply that a crossover from NFL/BEC to FL/BCS is driven by the change of electron correlation. In the present work, we investigated thermoelectric effects for κ-(ET)4Hg2.89Br8 under pressure. We found that, in the crossover pressure region, the Seebeck coefficient divided by temperature, S/T, is enhanced at low temperatures and its temperature dependence is logarithmic, suggesting that the present observation originates from NFL-FL quantum critical fluctuations. Regarding the superconductivity, the Nernst voltage is generated at higher temperature than Tc and keeps large values at higher magnetic fields in the low-pressure regime than in the high-pressure regime, indicating that superconducting fluctuations are strongly enhanced in the doped spin liquid state at low pressures.[1] H. Oike, et al., Nat. Commun. 8, 756 (2017). [2] H. Oike et al., Phys. Rev. Lett. 114, 067002 (2015). [3] Y. Suzuki, Master Thesis (2017).

P-Mo-34: HTSC as self-doping CT-excitonic insulators K. Mitsen1, and O. Ivanenko1 1Lebedev Physical Institute, Moscow 119991, Russia We have proposed a generalized model for the electronic structure of HTSC cuprates and ferropnictides, which treats these materials as charge transfer (CT) excitonic insulators (CT phase) with an intrinsic self-doping mechanism that provides the generation of free carriers. This mechanism is not directly related to external doping, but is due to the interaction of band electrons with so called Heitler–London (HL) centres inherently existing in the CT phase and representing pairs of adjacent CuO4 or AsFe4 plaquettes in the CuO2 or FeAs basal planes. Material in this state has been shown to represent a medium, where the mechanism of excitonic superconductivity can be realized. The role of doping according to the model consists in only a local change in the electronic structures of cuprates and ferropnictides, leading to the formation of a percolation cluster of the CT phase in material. The ranges of dopant concentrations conforming to the existence of percolation clusters of the CT phase have been determined; these ranges have been shown to coincide with the positions of the superconducting domes on the phase diagrams of these compounds. This coincidence may serve to prove the validity of the proposed model for the basic state of cuprate and ferropnictide HTSCs.

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P-Mo-35: Characterization of photoexcited states in the half-filled one-dimensional extended Hubbard model assisted by machine learning K. Shinjo1, S. Sota2, S. Yunoki2,3,4, and T. Tohyama1

1Department of Applied Physics, Tokyo University of Science, Tokyo 125-8585, Japan 2Computational Materials Science Research Team, RIKEN Center for Computational Science (R-CCS), Kobe, Hyogo 650-0047, Japan 3Computational Condensed Matter Physics Laboratory, RIKEN Cluster for Pioneering Research (CPR), Wako, Saitama 351-0198, Japan 4Computational Quantum Matter Research Team, RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan Photoinduced nonequilibrium states can provide new insights into the dynamical properties in strongly correlated electron systems. One of the typical and extensively-studied systems is the half-filled one-dimensional extended Hubbard model (1DEHM). Here, we propose that the supervised machine learning (ML) can give useful information for characterizing the photoexcited state in 1DEHM [1]. Using entanglement spectra as a training dataset, we construct the neural network. Based on the judgement of the trained network, we find the enhancement of the BSDW order in the photoexcited states for U = 2V, where U (V) is the on-site (nearest-neighbor) Coulomb interaction. The enhancement has never been reported previously, thus demonstrating the advantage of ML to assist characterizing photoexcited quantum states. [1] K. Shinjo, et al., arXiv: 1901.07900.

P-Mo-36: Superconductivity in the vicinity of odd-parity magnetic multipole order J. Ishizuka and Y. Yanase Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan Recent intensive research in locally noncentrosymmetric crystals has revealed that odd-parity

multipole order would be realized in several materials, such as Sr2IrO4 [1] and Cd2Re2O7 [2]. Superconductivity in the vicinity of odd-parity electromagnetic multipole order may invokes an unconventional pairing mechanism. Of cause, a lot of unconventional spin-singlet superconductors are classified in the locally noncentrosymmetric crystals, such as iron-based superconductors and CeCoIn5 superlattice. These superconducting states are stabilized by even-parity antiferromagnetic (nematic) fluctuations. The superconductivity induced by the odd-parity multipole fluctuation has not been explicitly investigated so far. Here, we investigate a two-sublattice Hubbard model with the sublattice-dependent antisymmetric spin-orbit coupling and Coulomb interaction [3]. We find that a magnetic quadrupole, hexadecapole, and toroidal fluctuations appear by the antisymmetric spin-orbit coupling. Furthermore, spin-triplet p+dxy- and p+s-wave states are realized near the odd-parity magnetic multipole order. [1] L. Zhao et al., Nat. Phys. 12, 32 (2016) [2] L. Fu, Phys. Rev. Lett. 115, 026401 (2015)

[3] J. Ishizuka and Y. Yanase, Phys. Rev. B 98, 224510 (2018).

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P-Mo-37: Superconductivity in Empty Bands and Multiple Order Parameter Chirality W. C. Wu1 and R. Joynt,2 1Department of Physics, National Taiwan Normal University, Taipei, 11677, Taiwan 2Department of Physics, University of Wisconsin-Madison, Madison, WI, 53706, USA Recent experiments have shown rotation of the plane of polarization of light reflected from the surface of some superconductors. The photon energy exceeds the electronic bandwidth, so that completely filled or completely empty bands must play a role. We show that in strong-coupling theory a Coulomb interaction can produce an order parameter in the unoccupied band that explains the observations. Thus the phenomenology puts tight constraints on the form of the order parameter in different bands. We propose that the experiments have detected, for the first time, the existence of a superconducting order parameter in a band far from the Fermi energy [1]. This is only possible because of the sensitivity to delicate symmetries: a positive Kerr effect indicates that time reversal and certain mirror symmetries are broken in the ordered phase. Furthermore, detailed analysis of the results implies that in UPt3 there exist bands that have different order parameter chiralities, opening up complex new possibilities for topological superconductivity.

[1] R. Joynt and W. C. Wu, Sci. Rep. 7, 12968 (2017).

P-Mo-38: Ultra-high Resolution Photoemission Spectroscopy with High Intensity CW Laser T. Nagashima, Y. Ota, T. Hashimoto, A. Tsuzuki, A. Fukushima, K. Okazaki, S. Shin The Institute for Solid State Physics, The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan

We have developed a high intensity CW laser for ultra-high resolution photoemission spectroscopy to observe superconducting gaps of low Tc unconventional superconductors. High energy resolution is generally attained with the setting of a narrow slit of an electron analyzer and narrow line width of a light source [1]. However, this causes deterioration of efficiency of experiments. Moreover, there is another problem of the space charge effect caused by high peak energy of pulse lasers, which does not allow the solution of inefficiency by increase of the laser power. Considering these, it is desirable to use a high intensity CW laser for the light source, of which low peak intensity and narrow line width enables high resolution measurements with the negligible space charge effect. We have confirmed that a spectrum with the energy resolution below 1 meV can be obtained within a few minutes, and also that angle-resolved measurements are available. [1] T. Shimojima, K. Okazaki, and S. Shin, J. Phys. Soc. Jpn. 84, 072001 (2015).

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P-Tu-1: Pauli-limit upper critical field of La1.84Sr0.16CuO4 investigated by high-frequency contactless transport measurements in megagauss fields Daisuke Nakamura1, Tadashi Adachi2, Keisuke Omori3, Yoji Koike3, and Shojiro Takeyama1 1 Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan 2 Department of Engineering and Applied Sciences, Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan 3 Department of Applied Physics, Graduate School of Engineering, Tohoku University, 6-6-05 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan The upper critical field of a high-temperature cuprate superconductor, La1.84Sr0.16CuO4, was investigated by the high-radio frequency self-resonant contactless transport measurements in magnetic fields up to 102 T, generated by the single-turn coil megagauss generator. The upper critical field was observed at 85 T as the irreversible superconducting-normal transition in magnetic fields. The Pauli-limiting pair breaking process with a small contribution from the spin-orbit coupling parameter explains the first-order phase transition exhibiting hysteresis observed at low temperatures.

P-Tu-2: Pseudogap behavior in T’-Pr1.3-xLa0.7CexCuO4 (x = 0.10) probed by NMR YS. Lee1, S. Kanamaru1, M. Goto1, H. Fukazawa1, Y. Kohori1, A. Takahashi2, T. Kawamata2, K. Kawabata3, K. Tajima3, T. Adachi3 and Y. Koike2 1 Dept. of Phys., Grad. Sch. of Sci., Chiba Univ., Chiba 263-8522, Japan 2 Dept. of Appl. Phys., Grad. Sch. of Eng., Tohoku Univ., Sendai 980-8579, Japan 3 Dept. of Eng. and Appl. Sci., Sophia Univ., Chiyoda, Tokyo 102-8554, Japan Mechanism of high Tc superconducting cuprates (HTSCs) has been studied since their

discovery, but is not completely understood yet. Hole-doped HTSCs were extensively studied. On the other hand, not so much work has been performed in electron-doped HTSCs because of the small superconducting region adjacent to antiferromagnetic region. However, an adequate annealing process, which removes apical oxygens in samples, enlarges SC region and reduces AF region [1, 2]. The phase diagram of electron-doped HTSCs becomes similar to that of hole-doped HTSCs. There are parity between electron- and hole-doped HTSCs [3]. We report the first observation of psuedogap behavior of electron-doped HTSCs probed by

NMR. In addition, we investigate the effect of dynamic annealing, which includes supplementary annealing process after protect-annealing, in x = 0.15 by comparing with the previous study [4]. [1] O. Matsumoto et al., Physica C 469, 924-927 (2009). [2] T. Adachi et al., J. Phys. Soc. Jpn. 82, 063713 (2013) [3] DJ. Song et al, Phys. Rev. Lett. 118, 137001 (2017). [4] M. Yamamoto et al, J. Phys. Soc. Jpn. 85, 024708 (2016).

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P-Tu-3: Charge density fluctuations and charge density waves rule the transport of cuprate high temperature superconductors R. Arpaia1,2, S. Caprara3, R. Fumagalli1, M. Rossi1, E. Andersson2, G. Seibold4, Y.Y. Peng1, D. Betto5, G. M. De Luca6,7, N. B. Brookes5, M. Salluzzo7, T. Bauch2, L. Braicovich1,5, C. Di Castro3, F. Lombardi2, M. Grilli3, G. Ghiringhelli1,7 1Dipartimento di Fisica, Politecnico di Milano, Milano, Italy; 2Department of Microtechnology and Nanoscience, Chalmers University, Göteborg, Sweden; 3Dipartimento di Fisica, Università La Sapienza, Roma, Italy; 4Institut für Physik, Cottbus, Germany; 5ESRF, Grenoble, France; 6Dipartimento di Fisica, Università Federico II, Napoli, Italy; 7CNR-SPIN, Italy;

Even though charge density waves (CDW) are a common occurrence in all families of high critical temperature superconducting cuprates (HTS), they are mainly observed in a restricted region of the phase diagram, thence it is still unclear to what extent they influence the properties of these systems. Using resonant x-ray scattering we discovered in (Y,Nd)Ba2Cu3O7-δ short-range charge density fluctuations (CDF) besides the previously known CDW. They persist up to well above the pseudogap temperature T*, are characterized by energies of few meV and pervade a large area of the phase diagram [1]. Remarkably, we found that CDF may explain the linear T dependence of the resistance above T*, indicating that they are likely the long-sought excitations underlying the anomalous Marginal Fermi Liquid behavior of HTS. CDW seem to dominate instead the transport below T*: indeed, we discovered that the strain-induced suppression of CDW in ultrathin YBa2Cu3O7-δ films strongly modifies the T dependence of the resistance below T*.

[1] R. Arpaia et al., arXiv:1809.04949 (2018). Accepted by Science (2019)

P-Tu-4: Role of the inner CuO2 plane in interlayer Josephson effects in multi-layered cuprate superconductors Bi2223 I. Kakeya1, Y. Nomura1, R. Okamoto1, T. Mizuno1, M. Suzuki1, S. Adachi2, and T. Watanabe2 1Department of Electronic Science and Engineering. Kyoto University, Kyoto 615-8510, Japan 2Graduate school of Science and Technology, Hirosaki University, Hirosaki 036-8224, Japan We find important systematic signatures suggesting a different nature of the order parameter for the inner CuO2 plane compared to the outer CuO2 planes of a triple-layered cuprate Bi2Sr2Ca2Cu3O10+δ. The properties of intrinsic Josephson junctions reveal that the c-axis maximum Josephson current density is sensitive to the superfluid density in outer planes while the superconducting gap remain unaffected. The fluctuation in gauge-invariant phase difference of an intrinsic Josephson junction implies that the inner plane completely shields the capacitive coupling between adjacent intrinsic Josephson junctions, which is essential for mono- and double-layered cuprates. These results warrant the development of a new intrinsic Josephson junction model that includes the distribution of order parameter inside the superconducting layer [1]. [1] Y. Nomura et al., submitted.

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P-Tu-5: Reduction annealing effects on longitudinal optical phonons in T’-type Pr1.4La0.6CuO4 investigated by inelastic x-ray scattering S. Asano1,2, T. Fukuda3, A. Q. R. Baron4, H. Uchiyama5, and M. Fujita2 1 Department of Physics, Tohoku University, Sendai 980-8578, Japan 2Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan 3Materials Sciences Research Center, Japan Atomic Energy Agency, Sayo, Hyogo, 679-5148, Japan 4Materials Dynamics Laboratory, RIKEN SPring-8 Center, Sayo, Hyogo 679-5148, Japan 5Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198, Japan In order to realize superconductivity in T’-structure R2-xCexCuO4 (R = rare earth element), both Ce substitution and post-annealing in reduction atmosphere are necessary. It is widely recognized that a small amount of oxygen is removed by annealing, resulting into a drastic change in physical property. However, the microscopic mechanism of annealing has not been fully understood yet. To investigate the annealing effects on the electronic states through longitudinal optical phonons, we investigate the phonon dispersion of as-grown and annealed Pr1.4La0.6CuO4 (PLCO) along the [ξ, 0, 0] direction using inelastic x-ray scattering. We found that the softening of the longitudinal phonon branches, which is related to Cu-O bond stretching mode, by annealing, similarly in superconducting Nd1.86Ce0.14CuO4 [1]. The softening indicates the carrier doping due to annealing.

[1] M. d’Astuto et al., Phys. Rev. Lett. 88, 167002 (2002).

P-Tu-6: Discontinuous transition from 90 K to 60 K phase in epitaxial YBa2Cu3Oy thin films tuned by in-situ oxygen annealing pressure T. Nojima, Y. Morisawa, H. Liang, and T. Ouchi Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan We repot the interfacial effect on the electronic state in the (001) oriented YBa2Cu3Oy thin films with thickness of 20-40 nm, which were epitaxially grown on a SrTiO3(100) substrates by RF sputtering followed by in-situ post annealing under various oxygen partial pressure PO2. We found a discontinuous transition of critical temperature Tc from 90 K to 60 K with decreasing PO2 at a critical pressure of 0.1 Torr. After keeping the 60 K plateau, Tc goes abruptly to zero with further decreasing PO2. The oxygen content y estimated from the Hall coefficient and the c-axis length from the x-ray diffraction also show discontinuous changes at PO2 = 0.1 Torr. Our results suggest that the pinning phenomenon of Tc [1] with two kinds of preferable values of 90 K and 60 K occurs at interface (or in thin films) due to the self-organization of y to stabilize two phases in the case of YBa2Cu3Oy thin films. We will discuss the comparison to the case of La2CuO4/La2-xSrxCuO4 interface showing the Tc pinning phenomenon in the overdoped region [2], and the relation to the bulk cuprates showing the additional ordered phase, such as CDW, in the region of Tc between 90 K and 60 K. [1] T. Misawa et al., Sci. Adv. 2, e1600664 (2016). [2] J. Wu et al., Nat. Mater. 12, 877 (2013).

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P-Tu-7: Light-induced new collective modes and quasiparticle excitations in La2-xBaxCuO4 S. J. Zhang1, Z. X. Wang1, T. Dong1, G. D. Gu2, and N. L. Wang1

1 International Center for Quantum Materials, Peking University, Beijing 100871, China 2 Brookhaven National Laboratory, Upton, NY 11973, USA In a cuprate superconductor, the superconducting layers are separated by the insulating ones, leading to an insulating manner along c-axis. In superconducting phase, Cooper pairs tunnel across the insulating layers, which can be observed as resistivity going down to zero and the appearance of Josephson plasmon edge in reflectivity. Here we report the light-induced new collective modes and quasiparticle excitations in La2-

xBaxCuO4 (x = 0.095, 0.11, 0.125) after excited by 1.28 μm pump. In superconducting phase, upon excitation by strong near-infrared pulses, the superconducting state is severely disturbed and incoherent quasiparticle excitations develop in the frequency regime above the static plasma edge. Subsequently, a Josephson plasma edge reappears at a frequency lower than the static Josephson plasma edge and a new light-induced edge emerges at a higher energy. The system goes into a new metastable superconducting phase with modulated Josephson coupling strengths accompanied by some incoherent quasiparticles. In stripe order phase of La2-

xBaxCuO4, an edge-like feature is derived in the transient reflectance spectrum along c-axis.

P-Tu-8: Gradual suppression of CDM in a heavily overdoped cuprate T. Gazdić1, Ivan Maggio-Aprile1, Genda Gu2, Christoph Renner1 1Department of Quantum Matter Physics, University of Geneva, 24 quai Ernest-Ansermet, 1211 Geneva, Switzerland 2Brookhaven National Laboratory, CMPMS Division, Upton, NY 11973-5000, USA The wide zoo of phases in Bi2Sr2CaCu2O8+d have been investigated for years[1]. A paper[2] showing a Fermi surface reconstruction simultaneous with disappearance of the charge density modulations(CDM) has established a quantum critical point in the phase diagram at a doping of p=0.19. We revisit the heavily overdoped(p=0.22) side of the phase diagram by means of scanning tunneling microscopy, revealing a non-abrupt disappearance of the CDM despite the observed hallmark of heavily overdoped samples confirming a reconstructed Fermi surface – antinodal scattering, prompting the question of whether the transitions are truly simultaneous. [1] B. Keimer, et al. Nature 518, 179 (2015) [2] K. Fujita, et al. Science 344, 612-616 (2014)

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P-Tu-9: A two-pronged approach to the cuprate pseudogap: comparing mode-coupling and first-principles results R. Markiewicz1, C. Lane1, Y. Zhang2, J.Furness2, B. Barbiellini1, J. Sun2, and A. Bansil1 1Department of Physics, Northeastern University, Boston MA 02115, USA 2Department of Physics, Tulane University, New Orleans LA, 70118, USA We have used density functional theory with recent advances in treating correlation effects to study the problem of the cuprate psedogap in YBa2Cu3O7 (YBCO7)[1]. The energy landscape obtained via a parameter free first-principles self-consistent treatment of charge, spin and lattice degrees of freedom is found to consist of a competition between many different nearly degenerate states. This landscape involves a mixture of antiferromagnetic and stripe states, with the lower-energy phases having a larger planar copper magnetic moment. In particular, the nonmagnetic phase has too high an energy to play any role in the low-energy properties of YBCO7. The contrasting behaviors of YBCO6 and YBCO7 are reminiscent of the Mott-Slater crossover found in a mode-coupling model of the cuprates[2]. I will demonstrate how these two approaches illuminate each other, leading to a picture of the pseudogap as a gapped paramagnetic metal with only short-range order over a broad temperature range. This work provides a realistic model for the cuprate pseudogap phase with implications for superconducting pairing and for other correlated materials. [1] Y. Zhang et al., arXiv:1809.8457. [2] R.S. Markiewicz et al., Scientific Reports 7, 44008 (2017).

P-Tu-10: Infrared Spectroscopic Studies on the Orbital Selective Physics in Iron-based Superconductor KFe2As2 X.G. Qiu 1, R. Yang1, Q.T. Sui1, Z.P. Yin2, Y.M. Dai3, C.C. Homes3 1Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 2Department of Physics, Beijing Normal University, Beijing, China 3Condensed Matter Physics and Material Science Division, Brookhaven National Laboratory, NY 11973, USA KFe2As2 is a heavily holed iron-based superconductor. It is reported that there is an incoherence to coherence crossover, resembling that observed in heavy fermion systems. We have measurements the optical and magnetic responses of KFe2As2 by far-infrared and magnetic torque measurements. Indeed an incoherence to coherence crossover is observed which demonstrates itself as the emergence of a Drude peak in the low temperature in the optical conductivity. Spectrum weight analysis shows that the emergent Drude weight comes from the spectrum weight transfer from high energy bound states. Theoretical calculation suggests that the crossover possibly comes from the delocalization of electrons in the dxy orbital. The similarity between the phenomena observed in KFe2As2 and those in heavy fermion systems are being discussed.

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P-Tu-11: Incoherent-coherent crossover and the pseudogap in Te-annealed superconducting Fe1+yTe1-xSex: A magnetotransport study T. Watanabe1, T. Otsuka1, S. Hagisawa1, Y. Koshika1, S. Adachi1, T. Usui1, N. Sasaki1, S. Sasaki1, S. Yamaguchi1, Y. Nakanishi2, M. Yoshizawa2, and S. Kimura3 1 Graduate School of Science and Technology, Hirosaki University, 3 Bunkyo, Hirosaki, 036-8561 Japan 2 Graduate School of Engineering, Iwate University, Morioka 020-8551, Japan 3 Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577 Japan Knowledge of the doping(x)-temperature(T) phase diagram of superconductors is well recognized to be crucial to understand the mechanism of high-Tc superconductivity. Here, we address this issue by conducting various magnetotransport measurements on Fe1+yTe1-xSex single crystals from which excess iron was sufficiently removed [1]. We found that crossover from the incoherent to the coherent electronic state and opening of the pseudogap occur at high temperatures (150 K for x = 0.2). This is accompanied by a more substantial pseudogap and the emergence of a phase with a multi-band nature at lower temperatures (below 50 K for x = 0.2) before superconductivity sets in. A comparison of these results with those of the as-grown (non-superconducting) samples implies that the coherent state accompanied by the pseudogap is needed for the occurrence of superconductivity in this system. [1] Y. Koshika, T. Usui, S. Adachi, T. Watanabe, K. Sakano, S. Simayi, and M. Yoshizawa, J. Phys. Soc. Jpn. 82, 023703 (2013).

P-Tu-12: Nonequilibrium dynamics of iron-based superconductor FeSe induced by mid-infrared light excitation N. Yoshikawa1, K. Isoyama1, K. Tomita1, N. Shikama2, T. Ishikawa2, F. Nabeshima2, A. Maeda2, and R. Shimano1,3 1Department of Physics, The University of Tokyo, Hongo, Tokyo 113-0033, Japan 2Department of Basic Science, The University of Tokyo, Meguro, Tokyo 153-8902, Japan 3Cryogenic Research Center, The University of Tokyo, Yayoi, Tokyo, 113-0032, Japan

In iron-based superconductors (FeSCs), the elucidation of the interplay between nematic order, antiferromagnetic order, and superconductivity is an important issue as well as the understanding of paring mechanism of superconductivity. Among FeSCs, FeSe provides a unique playground to study the role of nematicity, because it lacks the long-range magnetic order in the nematic phase. To investigate the nonequilibrium dynamics of superconductivity and nematicity, here we performed mid-infrared pump-terahertz (THz) probe spectroscopy of FeSe thin film. When the sample in the superconducting phase is excited by mid-infrared light (photon energy 0.5 eV),

the 1/w-like divergent behavior in the imaginary part of optical conductivity is transiently enhanced below 2 meV within 2 ps, which suggests the transient enhancement of superconductivity. The spectrum changes to Drude-like behavior at 4 ps after photo-excitation, indicating the thermalization of the electron system.

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P-Tu-13: Magnetic ground state of the second antiferromagnetic phase under pressure in LaFeAsO1-xHx probed by muon spin rotation M. Hiraishi1, K. M. Kojima2, H. Okabe1, S. Takeshita1, A. Koda1,3, R. Kadono1,3, S. Iimura4, S. Matsuishi4, and H. Hosono4,5 1Muon Science Laboratory and Condensed Matter Research Center, Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba, Japan 2TRIUMF, Center for Molecular and Materials Science, Vancouver, Canada 3The Graduate University for Advanced Studies (Sokendai), Tsukuba, Japan

4Insutitute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan 5Materials Research Center for Element Strategy, Tokyo Institute of Technology, Yokohama, Japan In this presentation, we report muon spin rotation experiment under a high pressure in polycrystalline sample of LaFeAsO1-xHx with x = 0.51 which exhibits structural and antiferromagnetic (AF) transition at 95, 92 K, respectively. We demonstrate that AF transition is strongly suppressed with increasing pressure in parallel with the behavior of structural transition which is also suppressed under a relatively low pressure of 1.5 GPa [1]. We also show that the AF transition becomes short-ranged under pressure. These features are in marked contrast with the case for the magnetic phase for x ≤ 0.05 where a robust AF order against pressure is reported. [1] K. Kobayashi, et al., Sci. Rep. 6, 39646 (2016).

P-Tu-14: Superconducting gap of NdFeAs(O,F) observed by Raman scattering spectroscopy Z.H.Tin1, A.Takemori1, S.Miyasaka1, and S.Tajima1 1Department of Physics, Osaka University, Osaka, 560-0034, Japan In the research field of iron-based superconductors (IBSs), it is important to clarify the superconducting gap symmetry. Since the IBSs have several hole and electron Fermi surfaces at the different k positions in Brillouin zone, we need momentum selective tools such as Raman scattering and angle resolved photoemission spectroscopy (ARPES) that can separately detect the charge responses on the hole or electron Fermi surfaces. NdFeAs(O,F) is one of the 1111-type systems with the highest Tc amongst IBSs, but its superconducting gaps have not been well studied by ARPES because of the polar crystal surface problem. In this study we have investigated Raman scattering spectra of NdFeAs(O,F) to clarify its superconducting gap feature. Single crystal of NdFeAs(O,F) with Tc~41K was successfully synthesized by high-pressure method. In the superconducting state, we observed the emergence of pair-breaking peak in both A1g and B2g symmetries. These pair-breaking peaks in A1g and B2g symmetries are

due to the superconducting gap on the hole Fermi surfaces around G point and on the electron ones around M point, respectively. The superconducting gap values on hole and electron surfaces, which have been estimated from the energy positions of these pair-breaking peaks, are ~11.7 meV and ~9.5 meV, respectively.

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P-Tu-15: Magneto-optical imaging of dilute vortex solid to liquid transformation in a disordered single crystal of Ba0.6K0.4Fe2As2 Ankit Kumar1, Sayantan Ghosh1, Tsuyoshi Tamegai2, S. S. Banerjee1*

1Department of Physics, Indian Institute of Technology, Kanpur-208016, India 2Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan We have studied the low-field vortex lattice melting in a single crystal of Ba0.6K0.4Fe2As2 using bulk magnetization measurements and high-sensitivity differential magneto-optical imaging (DMOI) technique. We have observed a significant jump in local magnetization ~ 3G at low fields and whose size decreases with increasing applied field. The observed melting phenomena is traced on a field temperature phase diagram and the behavior of the melting boundary partially obeys the Lindemann criteria based vortex melting phenomenon and is associated with a Lindemann number cL = 0.14. Scaling of the MT data from the bulk magnetization measurement shows that the dimensionality of melting vortex state is close to one. Angular dependence of bulk magnetization hysteresis measurement shows the presence of extended defects arranged in a plane extending through the sample thickness in the sample. Here we argue that in the weak intervortex interaction limit, reduced vortex dimensionality due to pinning by extended defect planes strongly enhances thermal fluctuations and promote low dimensional vortex melting in this pnictide system. [1] Ankit Kumar, Sayantan Ghosh, Tsuyoshi Tamegai, S. S. Banerjee (submitted, 2018).

P-Tu-16: Temperature-dependent s±↔s++ transitions in multiband Fe-based superconductors with impurities O. V. Dolgov1,2, V.A. Shestakov3, M.M. Korshunov3 1Donostia International Physical Center, San Sebastian, Spain 2Max-Planck-Institute für Festkörperforschung, Stuttgart, Germany 3Kirensky Institute of Physics, Federal Research Center KSC SB RAS, Krasnoyarsk, Russia We study the dependence of the superconducting gaps on both the disorder and the temperature within the two-band model for iron-based materials. In the clean limit, the system is in the s± state with the sign-changing gaps. Scattering by nonmagnetic impurities leads to

the change of sign of the smaller gap thus resulting in a transition from the s± to the s++ state with the sign-preserving gaps [1]. We show here that the transition is temperature-dependent,

thus, there is a line of s±→s++ transition in the temperature-disorder phase diagram [2]. There

exists a narrow range of impurity scattering rates, where the disorder-induced s±→s++ transition

occurs at low temperatures, but then the low-temperature s++ state transforms back to the s± state at higher temperatures. With increasing impurity scattering rate, temperature of such

s++→s± transition shifts to the critical temperature Tc and only the s++ state is left for higher amount of disorder. [1] D.V. Efremov, M.M. Korshunov, O.V. Dolgov, A.A. Golubov, P.J. Hirschfeld, Phys. Rev. B 84, 180512(R) (2011) [2] V. A. Shestakov, M. M. Korshunov, O. V. Dolgov, Symmetry 10, 323 (2018)

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P-Tu-17: Frustrated spin order and orbital selectivity in FeSe A. Baum1,2, H. N. Ruiz3,4, N. Lazarević5, Yao Wang3,6, T. Böhm1,2, R. Hosseinian Ahangharnejhad1,2, P. Adelmann7, T. Wolf7, Z. V. Popović5,8, B. Moritz3, T. P. Devereaux3,9, and R. Hackl1

1 Walther Meissner Institut, BAdW, 85748 Garching, Germany. 2 Fakultät für Physik E23, Technische Universität München, 85748 Garching, Germany. 3 SIMES, SLAC National Accelerator Laboratory, CA 94025, USA. 4 Department of Physics, Stanford University, Stanford, CA 94305, USA. 5 Institute of Physics Belgrade, University of Belgrade, 11080 Belgrade, Serbia. 6 Department of Applied Physics, Stanford University, Stanford, CA 94305, USA. 7 KIT, Institut für Festkörperphysik, 76021 Karlsruhe, Germany. 8 Serbian Academy of Sciences and Arts, 11000 Belgrade, Serbia. 9 Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA. The separation of nematic and magnetic order in FeSe creates a unique opportunity to study these phenomena. We use Raman spectroscopy [1] and exact diagonalization of a spin-1 Heisenberg model [2] and show that the dominating response above 50 meV originates from localized spins. Our simulations create a link to neutron scattering and provide evidence for nearly frustrated stripe-order. We argue that these results indicate the important role of Hund- type physics in FeSe inducing orbital selective localization. [1] A. Baum et al., Commun. Phys. 2, 14 (2019) [2] H. N Ruiz et al., Phys. Rev. B99, 125130 (2019)

P-Tu-18: Substitution Effects in Ultrathin Iron-based Superconductor Films Studied by High-Resolution ARPES K. Nakayama1, K. Shigekawa1, K. Owada1, G. N. Phan1, T. Takahashi1,2,3, and T. Sato1,2,3 1Department of Physics, Tohoku University, Sendai 980-8578, Japan 2WPI-AIMR, Tohoku University, Sendai 980-8577, Japan 3CSRN, Tohoku University, Sendai 980-8577, Japan The discovery of high-temperature (Tc) superconductivity above 65 K in monolayer FeSe film on SrTiO3 substrate [1] has generated tremendous attention because the Tc value is surprisingly high and the material is an atomically thin (a few angstrom thick) film. To search for higher Tc and also to clarify the mechanism of high-Tc superconductivity, further studies on monoalyer films of other iron-based superconductors are highly required. In this study, we have grown chalcogen-substituted monolayer films on SrTiO3 by molecular-beam epitaxy and determined the electronic structure by high-resolution angle-resolved photoemission spectroscopy. We observed substitution-induced changes in the Tc value, Fermi-surface shape, and band width. We also found a signature of interfacial electron-phonon coupling. We discuss the implications of our results in relation to the high-Tc mechanism of atomically-thin iron-based superconductors. [1] Q.-Y. Wang et al., Chin. Phys. Lett. 29, 037402 (2012).

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P-Tu-19: A single full gap with mixed type-I and type-II superconductivity on surface of the type-II Dirac semimetal PdTe2 by point-contact spectroscopy Tian Le1, Qi Huang1, Zili Feng2, Liqiang Che1, Lichang Yin1, Youguo Shi2,3, and Xin Lu 1,5

1Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, China 2Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 3School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China 5Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China We report our point-contact spectroscopy (PCS) study on the superconducting state of the type-II Dirac semimetal PdTe 2 with a superconducting transition temperature T c ∼ 1.65 K. Our results show a consistent double-peak structure and they can be perfectly fitted by a single s-wave gap based on the Blonder-Tinkham-Klapwijk model. The gap follows a typical Bardeen-Cooper-Schrieffer temperature behavior, yielding ∆0 ∼ 0.29 meV and 2∆0 /kBTc = 4.15 in the strong coupling regime. A sudden suppression of the superconducting gap in magnetic field

around Hc ∼ 130 Oe is observed for most point-contacts on PdTe 2 , characteristic of a first-order transition for type-I superconductor in field. However, for other contacts, a smooth evolution of the PCS conductance persists up to H c ∼ 600 Oe, signaling a local type-II superconductivity. The observed admixture of type-I and type-II superconductivity can possibly arise from an inhomogeneous electron mean free path on the surface of PdTe2 due to its topological surface states.

P-Tu-20: Edge currents as a probe of the strongly spin-polarized topological noncentrosymmetric superconductors

M. Biderang1, M. H. Zare2, P. Thalmeier3, and A. Akbari1 1Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea 2Department of Physics, Faculty of Science, Qom University of Technology, Qom, Iran 3Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany Recently the influence of antisymmetric spin-orbit coupling has been studied in novel topological superconductors such as half-Heusler compounds and artificial heterostructures. We investigate the effect of Rashba and/or Dresselhaus spin-orbit couplings on the band structure and topological properties of a two-dimensional noncentrosymmetric superconductor. To explore the transport properties, we examine the response of the spin-polarized edge states to an exchange field in a superconductor-ferromagnet heterostructure. The broken chiral symmetry causes the unidirectional currents at opposite edges. We propose the existence of a substantial charge current parallel to the interface between a noncentrosymmetric superconductor and a metallic ferromagnet. We derive an expression for the interface current a long with a systematic study of the current considering the qualitative differences between the gapped and gapless superconductors, which reflect the very different underlying topological properties[1]. [1] M. Biderang, et. al, Phys Rev B 98, 014524 (2018).

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P-Tu-21: Observation of Superconducting gap and vortices in BiCh2 materials S. Demura1, S. Shobu2, K. Miyata2, S. Kaneko3, S. Okuma3 and H. Sakata2 1Department of Physics, College of science and technology, Chyoda-ku, Tokyo 101-8308, Japan 2Department of Physics, Tokyo University of Science, Shinjyuku-ku, Tokyo 162-8601, Japan Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8550, Japan

Layered BiCh2 superconductors (Ch=S, Se) show the novel properties owing to the crystal structure, which is analogous to that of cuprates and iron-based superconductors [1,2]. Therefore, evaluation of superconducting properties such as the superconducting gap and the vortices are important to elucidate the mechanism of the superconductivity. However, the measurements to evaluate these properties are difficult due to the relative lower superconducting transition temperature (Tc) of these superconductors. Recently, it was found that the Tc of La(O,F)BiS2, which is one of the BiCh2 superconductors, is increased by partial substitution of the other ions for Bi ions. By using the single crystal samples prepared by this technique, the observation of the superconducting gap was succeeded with scanning tunneling spectroscopy (STS). Furthermore, vortices were observed under the magnetic field. In this presentation, the detail of these results will be discussed.

[1] S. Demura, Nov. Supercond. Mat. 2, 1 (2016). [2] S. Demura, J. Phys. Soc. Jpn 88, 041002 (2019).

P-Tu-22: Observation of topologically protected surface states in Bi-Pd alloy superconductors M. Sakano1, K. Okawa2, M. Kanou2, Y. Kubota1, H. Sanjo1, E. F. Schwier3, K. Shimada3, T. Okuda3, T. Sasagawa2, and K. Ishizaka1,4 1Quantum-Phase Electronics Center (QPEC) and Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan 2Materials and Structures Laboratory (MSL), Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan 3Hiroshima Synchrotron Radiation Center (HiSOR), Hiroshima University, Higashi-hiroshima, Hiroshima 739-0046, Japan 4RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Saitama, Japan

Centrosymmetric bismuth-palladium alloy superconductors (a- and b-PdBi2[1]) are investigated by spin- and angle-resolved photoemission spectroscopy. Beside the spin-degenerate bulk bands, several spin-polarized surface bands, some of which crossing the Fermi level and isolated from the bulk bands in momentum space, are clearly observed. These surface states are evaluated to be topologically protected, based on the Z2 invariant derivation in analogy to 3-dimensional strong topological insulators. It indicates that these materials are likely to be topological superconductors realized without any carrier doping or applying pressure. [1] M. Sakano, et al., Nat. Commun. 6, 8595 (2015).

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P-Tu-23: Optical conductivity of granular aluminum films near the metal to insulator transition: towards a BCS-BEC crossover Aviv Glezer Moshe1,2, Eli Farber1,2, and Guy Deutscher1 1 School of Physics and Astronomy, Tel Aviv University, Israel. 2 Department of Physics and Department of Electrical and Electronic Engineering, Ariel University, P.O.B. 3, Ariel 40700, Israel. We report measurements of the energy gap of granular aluminum films by THz spectroscopy [1]. We find that as the grains progressively decouple, the coupling ratio 2∆(0)/kBTc increases above the BCS weak coupling ratio 3.53, and reaches a values consistent with a BCS-BEC crossover for the high resistivity samples. The Mattis-Bardeen (MB) formalism describes remarkably well the behavior of σ1,s /σ1,n for all samples up to very high normal state resistivities. Further, a detailed comparison is made with NbN [2] which suggests that the nature of the metal to insulator is not the same. While it is of the Anderson type in NbN [3], we believe that it is of the Mott type in granular Al, as already proposed [4]. We argue that it is consistent with the large value of the coupling ratio. [1] AG Moshe, E Farber, G Deutscher, arXiv:1901.02814 (2019). [2] B. Cheng et al., Phys. Rev. B 93, 180511 (2016). [3] M. Mondal et al., Phys. Rev. Lett. 106, 047001 (2011). [4] N. Bachar et al., Physical Review B 91, 041123 (2015).

P-Tu-24: Approaching BCS-BEC crossover in gate-controlled 2D superconductors Y. Nakagawa1, Y. Saito1, T. Nojima2, K. Inumaru3, S. Yamanaka3, Y. Kasahara4, and Y. Iwasa1,5 1The University of Tokyo, Tokyo 113-8656, Japan 2Tohoku University, Sendai 980-8577, Japan 3Hiroshima University, Higashi-Hiroshima 739-8527, Japan 4Kyoto University, Kyoto 606-8502, Japan 5RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan Electrical control of two-dimensional (2D) superconductivity has been attracting enormous interests as represented by SrTiO3 and magic-angle twisted bilayer graphene [1]. In this presentation, we demonstrate that the gate-control of electrochemical intercalation processes offers a new opportunity to study exotic phenomena in 2D superconductors [2]. In the low carrier-density limit of layered nitrides (ZrNCl and HfNCl), associated with the enhancement of critical temperature Tc, the system is located close to a crossover region from the Bardeen-Cooper-Schrieffer (BCS) limit to the Bose-Einstein condensation (BEC) limit. Its features are detected both by transport measurements and tunneling spectroscopies. This work sheds new light on the exploration of 2D superconductors. [1] Y. Cao et al., Nature 556, 43-50 (2018). [2] Y. Nakagawa et al., Phys. Rev. B 98, 064512 (2018).

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P-Tu-25: Enhancing superconductivity in alkali-doped fullerides Yusuke Nomura RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan Recently, Mitrano et al. [1] reported possible light-induced superconductivity in K3C60 up to a high-temperature of about 100 K – much above the equilibrium critical temperature ~ 20 K. In the equilibrium situation, it has been shown that the alkali-doped fullerides have unusual form of the intramolecular interaction with strongly-repulsive Hubbard and weakly negative exchange interactions [2]. The effective negative exchange interaction is induced by Jahn-Teller phonons. This unusual situation leads to surprising cooperation between Coulomb interactions and phonons to realize s-wave superconductivity [2]. Here, we study the effect of perturbations, which will be induced by a mid-infrared femto-second light-pulse [3]. We demonstrate that an “interaction imbalance” (two orbitals having smaller Hubbard interactions compared to the third orbital) efficiently enhances superconductivity. The physical mechanism responsible for the enhanced superconductivity is the stabilization of states containing singlet Cooper pairs coherently delocalized between two orbitals having smaller Hubbard interactions [3]. This work is done in collaboration with Minjae Kim, Michel Ferrero, Priyanka Seth, Olivier Parcollet, and Antoine Georges. [1] M. Mitrano et al., Nature 530, 451 (2016) [2] Y. Nomura et al., Sci. Adv. 1, e1500568 (2015); J. Phys.: Condens. Matter 28, 153001(2016) [3] M. Kim et al., Phys. Rev. B 94, 155152 (2016)

P-Tu-26: Ferromagnetic Superconducting Nanodiamond

T. Samuely1, G. Zhang2, O. Onufriienko1, A. Volodin3, N. Iwahara3, L. F. Chibotaru3, V. V. Moshchalkov3, P. Szabó1, and P. Samuely1 1Centre of Low Temperature Physics, IoEP SAS & FoS UPJŠ in Košice, Slovakia 2NanoSYD, MCI & DIAS, University of Southern Denmark, Sonderborg, Denmark 3INPAC, TNG & LSSPM, KU Leuven, Belgium Hydrogenation of diamond can induce intrinsic ferromagnetism, while boron doping can induce superconductivity. Our study of boron-doped diamond nanostructures with hydrogenated surfaces revealed a startling coexistence of both commonly antagonistic phenomena.[1] More recently, a thorough study of the spatial distribution of local density of states disclosed in-gap states extending over tens of nanometers. A tentative microscopic model of the Yu-Shiba-Rusinov bands in a 3D superconductor with a 2D spin lattice on its surface accurately reproduced our experimental measurements. These findings suggest that apart from the Fulde-Ferrell-Larkin-Ovchinnikov state and the domain wall superconductivity, Yu-Shiba-Rusinov effect can be another microscopic mechanism behind the coexistence of ferromagnetism and superconductivity. [1] G. Zhang, T. Samuely et al., ACS Nano 11, 5358 (2017)

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P-Tu-27: Irreversible metal-insulator transition in thin film VO2 induced by soft X-ray irradiation V. R. Singh Department of Physics, Central University of Kashmir, Srinagar, Jammu And Kashmir 190004, India In this study, we show the ability of soft x-ray irradiation to induce room temperature metal insulator transitions (MITs) in VO2 thin films grown on R-plane sapphire. The ability of soft x-rays to induce MIT in VO2 thin films is confirmed by photoemission spectroscopy and soft x-ray spectroscopy measurements. When irradiation was discontinued, the systems do not return to the insulating phase. Analysis of valence band photoemission spectra revealed that the density of states (DOSs) of the V 3d band increased with irradiation time, while the DOS of the O 2p band decreased. We use these results to propose a model in which the MIT is driven by oxygen desorption from thin films during irradiation.

P-Tu-28: Impurity Effects on the Superconductivity in LaO0.5F0.5BiS2 Y. Wang1, N. Momono1, T. Tamura1, H. Ohta1, S. Takeyabu1, K. Nara1, T. Kurosawa2, M. Oda2, and M. Ido2 1Muroran Institute of Technology, Muroran, 050-8585, Japan 2Hokkaido University, Sapporo, 060-0808, Japan Since the discovery of superconductivity in layered material LaOxF1-xBiS2, it has attracted so much attention of many researchers. The reason of that is the crystal structure is analogous to those of high-temperature cuprate and Fe-based superconductors. The superconducting gap symmetry and the bulk nature of superconductivity will reflect the origin of superconducting mechanism. Because of that, we investigated the impurity effects in the typical BiS2 superconductor LaO0.5F0.5BiS2 by specific heat measurement. Single crystals of LaO0.5F0.5Bi1-

ySbyS2 were grown by using CsCl/KCl-flux method under ambient pressure. The electronic specific heat was obtained by subtracting the lattice contribution βT3 from the total specific heat C(T). The results of electronic specific heat show the bulk nature of superconductivity in these compounds and the superconducting gap suggest being full gap with s-wave in weak-coupling limit despite the suppression of Tc due to an impurity scattering.

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P-Tu-29: Anomalous lattice contraction and emergent phases in (Eu1-xBix)2Ir2O7 G. Prando1, P. Telang2, K. Mishra2, A. K. Sood3, S. Singh2,4 1Department of Physics, University of Pavia, 27100 Pavia, Italy 2Department of Physics, IISER, 411008 Pune, India 3Department of Physics, Indian Institute of Sciences, 560012 Bangalore, India 4Center for Energy Sciences, IISER, 411008 Pune, India We report on our recent study of the pyrochlore series (Eu1-xBix)2Ir2O7 for polycrystalline samples for 0 ≤ x ≤ 1 [1]. We show that the lattice undergoes an anomalous contraction for x ≤ 0.05 but that the magnetic all-in/all-out state remains robust in that limit of chemical dilutions. We compare these findings with our previous results about the robustness of the magnetic state in Eu2Ir2O7 as a function of external hydrostatic pressure [2]. For small x values, the resistivity approaches a 1/T dependence at low temperatures, suggesting a proximity to the Weyl semimetallic phase, as predicted theoretically. At x = 0.1 a qualitatively new ground state emerges, which is characterized by a metalllic behaviour and absence of magnetic ordering at least down to 20 mK. For higher Bi-doping values, the resistivity remains metallic and it evolves gradually from T-like to T2-like and, eventually, to T3/2-like, suggesting the possibility of a variety of novel exotic electronic phases between Eu2Ir2O7 and Bi2Ir2O7. [1] P. Telang, K. Mishra, G. Prando, A. K. Sood, and S. Singh, arXiv:1902.03214 (2019). [2] G. Prando et al., Phys. Rev. B 93 104422 (2016).

P-Tu-30: X-ray study of ultrafast spin dynamics of transition-metal compounds H. Wadati1,2 1 Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan 2 Graduate School of Material Science, University of Hyogo, Ako, Hyogo 678-1297, Japan Control of spin states by optical excitations in magnetically ordered materials has attracted considerable attention since the ultrafast demagnetization in Ni was observed within 1 picosecond (ps). Time-resolved x-ray magnetic circular dichroism (trXMCD) can provide information on element-specific spin dynamics. X-rays from synchrotron radiation (SR) have time structures related to the SR pulse width of several 10 ps. X-ray free electron laser (XFEL) creates intense ultra-short (fs) x-ray pulses, enabling much more detailed study of the dynamics of the materials. We performed trXMCD measurements in a pump-probe setup by using SR in SPring-8 BL07LSU [1] and XFEL in SACLA BL3 [2]. The pump light is Ti:sapphire laser (800 nm), and the probe is SR or XFEL. In the case of L10-FePt thin films (20 nm) on MgO (100) substrates, we found that Fe was demagnetizing much faster than Pt, which was characterized by the different demagnetization times, Fe: 0.1 ps and Pt: 0.6 ps. This large difference might be related to the mechanism of all-optical helicity-dependent switching observed in FePt granular. [1] K. Takubo, H. Wadati et al., Appl. Phys. Lett. 110, 162401 (2017). [2] K. Yamamoto, H. Wadati et al., arXiv:1810.02551v1.

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P-Tu-31: Observation of the electronic structures in the misfit superconductors (PbSe)1.16(TiSe2)n (n = 2, 3) K. Takahashi1, T. Ueno2, I. Araya1, M. Kitamura3, K. Horiba3, H. Kumigashira3, T. Shimojima4, M. Sakano1, K. Kobayashi2,5, J. Akimitsu5 and K. Ishizaka1,4

1Department of Applied Physics, University of Tokyo, Tokyo 113-0033, Japan 2Department of Physics, Okayama University, Okayama 700-8530, Japan 3Photon Factory, Insititute of Material Structure Science, High Energy Accelerator Research Organization (KEK), Tsukuba 305-0801, Japan 4RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan 5Research Institute for Interdisciplinary Science, Okayama University, Okayama 700-8530, Japan Misfit compounds (PbSe)1.16(TiSe2)n (n = 2, 3) have peculiar crystal structures consisting of rock-salt PbSe and 1T-TiSe2 layers stacking alternately. Although bulk PbSe and TiSe2 by themselves do not show any superconductivity, their misfit compounds exhibit the superconducting transitions at around 2 K [1]. To reveal the origin, we investigate the electronic structures by using angle-resolved photoemission spectroscopy. Observed Fermi surfaces and band dispersions mainly reflect the character of TiSe2, and these indicate the electron transfer to the TiSe2 layer of 11% (n = 2) and 8.4% (n = 3), respectively. These results are consistent with the superconductivity appearing in the electron doped bulk CuxTiSe2[2]. On the other hand, additional elliptical Fermi surface is observed for the n = 2. This Fermi surface is seemingly unique to the misfit structure, possibly contributing to the superconductivity. [1] N. Ginag et al., Phys. Rev. B 82, 024503 (2010). [2] E. Morosan et al., Nat. Phys. 2, 544 (2006).

P-Tu-32: Point contact spectroscopic study of the pressure dependence of the superconducting gap on Sn metal M. Kuninaka1, G. Motoyama1, M. Adachi1, T. Mutou1, S. Nishigori1,2, K. Miyoshi1 and K. Fujiwara1 1 Department of Material Science, Shimane University. 2 ICSR, Shimane University. Point-contact spectroscopy on BCS superconductor tin have been measured in order to reveal

the D0-Tc relation under pressure, where D0 is the superconducting gap energy, and Tc is the critical temperature. Temperature variation of the point-contact spectrum of the

superconducting state was observed at several pressure. We obtained a valid D0 for each spectrum from comparison with calculation results based on the Blonder-Tinkham-Klapwijk theory. The calculated results well reproduce the temperature variations of the point-contact

spectrum. When Tc decreases with increasing pressure, D0 decreases while keeping the relation

of D0 / kBTc = 1.76.

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P-Tu-33: Heavy quasiparticle bands in the underscreened quasiquartet A. Akbari, and T. Thalmeier, 1 Asia Pacific Center for Theoretical Physics, POSTECH, Pohang, Korea

2 Max Planck Institute for Chemical Physics of Solids, Dresden, Germany We study the quasiparticle spectrum in an underscreened Kondo-lattice (KL) model that involves a single spin degenerate conduction band and two crystalline-electric-field (CEF) split Kramers doublets coupled by both orbital-diagonal and non-diagonal exchange interactions. We find the three quasiparticle bands of the model using a constrained fermionic mean field approach. While two bands are similar to the one-orbital model a new genuinely heavy band inside the main hybridization gap appears in the quasiquartet model. Its dispersion is due to effective hybridization with conduction states but the bandwidth is controled by the size of the CEF splitting. Furthermore several new indirect and direct hybridztion gaps may be identified. By solving the selfconsistency equation we calculate the CEF-splitting and exchange dependence of effective Kondo low energy scale, hybridization gaps and band widths. We also derive the quasiparticle spectral densities and their partial orbital contributions. We suggest that the two-orbital KL model can exhibit mixed CEF/Kondo excitonic magnetism. [1] Phys. Rev. B 98, 155121 (2018).

P-Tu-34: Gauge-invariant microscopic kinetic theory of superconductivity in response to electromagnetic fields II: Application to collective modes Fei Yang University of Science and Technology of China We show that the gauge-invariant kinetic equation of superconductivity provides an efficient approach to study the electromagnetic response of the gapless Nambu-Goldstone and gapful Higgs modes on an equal footing. We prove that the Fock energy in the kinetic equation is equivalent to the generalized Ward's identity. Hence, the gauge invariance directly leads to the charge conservation. Both linear and second-order responses are investigated. The linear response of the Higgs mode vanishes in the long-wave limit. The linear response of the Nambu-Goldstone mode is in consistency with the previous works. Whereas the second-order response exhibits interesting physics. On one hand, a finite second-order response of the Higgs mode is obtained in the long-wave limit. We reveal that this response, which has been experimentally observed, is attributed solely to the drive effect rather than the widely considered Anderson-pump effect. On the other hand, the second-order response of the Nambu-Goldstone mode, free from the influence of the long-range Coulomb interaction and hence the Anderson-Higgs mechanism, is predicted. We find that both Anderson-pump and drive effects play important role in this response. A tentative scheme to detect this second-order response is proposed.

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P-Tu-35: Edge current induced superconducting Edelstein effect Y. Ikeda, and Y. Yanase Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan Controlling of magnetic moments using local electric current is an important topic in

the modern field of spintronics. One of the representative methods is the Edelstein effect [1].

However, for practical applications, it is widely known that quite large amount of current

density is needed. Therefore, Joule heating created by dissipative current is a main obstacle for

efficient control of magnetization.

In this study, we suppose that the surface state of d-wave superconductors is a good

candidate for efficient magnetization control. D-wave superconductors show topologically

nontrivial properties [2], and is accompanied by unique surface band structure, e.g. Majorana

flat band in its edge mode [3]. In this study, we have found the high efficient spin accumulation

by super current in its edge state.

[1] V. M. Edelstein, Phys. Rev. Lett. 75, 2004 (1995). [2] X. L. Qi et al, Rev. Mod. Phys. 13, 1057 (2011). [3] K. Yada, M. Sato, and T. Yokoyama, Phys. Rev. B 83, 064505 (2011).

P-Tu-36: The staggered flux state with nematic charge-density order for the pseudogap phenomena S. Fukuda1, K. Yamazaki1, H. Tsuchiura1, 2, and M. Ogata3 1Department of Applied Physics, Tohoku University, Aoba, Sendai 980-8579, Japan 2Center for Spintronics Research Network, Tohoku University, Sendai 980-8577, Japan 3Department of Physics, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan Recent experimental studies of cuprate superconductors have pointed out that the onset of the pseudogap (PG) is accompanied by broken translational [1] or C4 [2] symmetry, which implies that there exists charge-density or electron-nematic order in the PG region of the phase diagram. Since many of the features found in the PG state such as the Fermi arc are known to be well described by the staggered flux (SF) phase, it is interesting to clarify whether these broken symmetries are also due to the SF phase or not. In this contribution, we examine the stability of the spatially modulated SF state within the renormalized mean-field theory based on the t-J model with the nearest-neighbor Coulomb repulsion. We find that the SF state with nematic modulation can be stabilized, and also that it can coexist with d-wave superconducting order. [1] B. Keimer, et al., Nature 518, 179-186 (2015). [2] Y. Sato, et al., Nature Phys. 13, 1074-1078 (2017).

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P-Tu-37: Spontaneously-broken rotational symmetry induced by backscattering interaction in a bond-alternated two-dimensional electron system Y. Takeoka, T. Sugimoto, and T. Tohyama Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan� Recently, electronic nematic states where a real-space rotational symmetry is spontaneously broken, have been observed in iron-based or copper oxide high-temperature superconductors [1]. A possible scenario is given by a Pomeranchuk instability due to d-wave forward-scattering interaction [2]. Here we present another possibility of spontaneously-broken rotational symmetry. Together with forward-scattering, we investigate an effect of backscattering interaction. In this model, a bipartite sublattice with a broken translational symmetry is formed by the backscattering. Focusing on the spontaneously-broken rotational symmetry, we also introduce a bond alternation consistent with the bipartite sublattice. Mean-field analysis on this model shows a spontaneously-broken rotational symmetry induced by the backscattering interaction such as the nematic transition caused by the forward-scattering. [1] Y. Sato et al., Nat. Phys. 13, 1074 (2017). [2] H. Yamase, Phys. Rev. B 91, 195121 (2015).

P-Tu-38: Topological interpretation of the Luttinger theorem Kazuhiro Seki1 and Seiji Yunoki1,2,3 1RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan 2RIKEN Cluster for Pioneering Research (CPR), Wako 351-0198, Japan 3RIKEN Center for Computational Science (R-CCS) Wako 351-0198, Japan Based solely on the analytical properties of the single-particle Green's function of fermions at finite temperatures, we show that the generalized Luttinger theorem inherently possesses topological aspects. The topological interpretation of the generalized Luttinger theorem can be introduced because (i) the Luttinger volume is represented as the winding number of the single-particle Green's function and, thus, (ii) the deviation of the theorem, expressed with a ratio between the interacting and noninteracting single-particle Green's functions, is also represented as the winding number of this ratio. The formulation based on the winding number naturally leads to two types of the generalized Luttinger theorem. This formulation also allows us to derive a sufficient condition for the validity of the Luttinger theorem of the first type by applying the Rouche's theorem in complex analysis as an inequality. All these general statements are made possible because of the finding that the Luttinger volume is expressed as the winding number of the single-particle Green's function, for which the complex analysis can be readily exploited [1].

[1] Kazuhiro Seki and Seiji Yunoki, Phys. Rev. B 96, 085124 (2017).

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P-Tu-39: Transition temperature and quasi-particle structure in dirty superconductors Takayuki Tamai1, Masaki Umeda2, and Masaru Kato1,2, 1 Department of Physics and Electronics, Osaka Prefecture University, Gakuencho, Nakaku, Sakai, Osaka 599-8531, Japan 2 Department of Mathematical Sciences, Osaka Prefecture University, Gakuencho, Nakaku, Sakai, Osaka 599-8531, Japan Superconducting transition temperature Tc depends on material structure and size as well as material parameters, such as atomic lattice structure. We showed microscopically transition temperature is enhanced for nano-sized and/or dirty superconductors, solving the the Gor’kov equation Bogoliubov-de Gennes (BdG) equations or with the finite element method [1,2,3]. We found for smaller and thinner superconductors show higher Tc. Also, for dirty superconductor, Tc is more enhanced for more localized Cooper pairs. In this study, we show the quasi-particle structures in these enhanced superconducting states in the nano-sized dirty superconductors. Also, we obtain the vortex states in dirty superconductors under an external field. We show the peculiar quasi-particle structures around a vortex in these superconductors.

[1] M. Umeda, M. Kato, and O. Sato IEEE Trans. Appl. Supercond. 26, 8600104 (2016).

[2] M. Umeda, and M. Kato, Physica C 560, 45 (2019).

P-Tu-40: A dilution refrigerator-cooled sample in steady 26T on a neutron beamline E. M. Forgan1, E. Blackburn1, 3, R. Wahle2, S. Gerischer2 and B. Klemke2

1School of Physics & Astronomy, University of Birmingham, Birmingham B15 2TT U.K. 2Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany 3Department of Physics, University of Lund, Box118, 22 100, Lund, Sweden We have constructed a horizontal dilution refrigerator (DR) operating with base temperature ~85 mK on the EXED neutron beamline at the BER-II neutron source at HZB Berlin. The 26T field of EXED gives the largest B / T ratio available on any neutron scattering instrument, and can provide a unique facility for investigating elastic, small-angle and inelastic scattering properties of unconventional superconductors and magnetic materials until the shutdown of BER-II. The DR design uses the double mixture injection concept, previously used in the Birmingham 17 T beamline cryomagnet [1]. This allows the DR to operate in the cryostat vacuum and gives very rapid cooling of the DR. We have addressed three problems arising from a high field hybrid magnet. (i) A silver alloy mixing chamber (MC) is used to give low nuclear heat capacity in field. (ii) The 3He still is situated >17 cm higher than the MC, so that the mixture is not expelled by diamagnetic forces. (iii) Vibrations due to the flow of cooling water in the copper insert of the magnet and ripple in the magnetic field value can give eddy-current heating. We have made the DR very rigid, and copper thermal shields at ~3 K shield out eddy currents and also damp out vibrations. [1] A.T. Holmes et al, Review of Scientific Instruments 83, 023904 (2012).

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P-Th-1: Fractional statistics of charge carriers of the t-J model and the Fermi Surface of cuprates P.A. Marchetti1, Y. Fei2, L. Yu3 and Z.B. Su4 1Dipartimento di Fisica e Astronomia , INFN, I-35131 Padova, Italy 2 Department of Physics, South University of Science and Technology of China, Shenzhen 518055, China, 3Institute of Physics, Chinese Academy of Sciences, 100190 Beijing, China, 4Institute of Theoretical Physics, Chinese Academy of Sciences, 100190 Beijing Using the spin-charge decomposition in the 1D t-J model the correct Fermi volume is recovered by imposing a fractional ½ Haldane exclusion statistics to the spinless charge carriers. We show that a similar result can be obtained in the t-J model in two dimensions, modeling the CuO planes in cuprates, using the techniques developed in [1]. As consequence a transition from small Fermi arcs to a large Fermi surface as doping increases is derived and the resulting composite nature of the hole, made of charge and spin carriers only weakly bounded, can provide a natural explanation of many unusual experimental features of the hole-doped cuprates [2]. [1] F. Ye, P.A. Marchetti, Z.B. Su and L. Yu, Phys. Rev. B92, 235151 (2015). [2] P.A. Marchetti, in Topological Phase Transitions and New Developments (World Scientic, Singapore 2018); arXiv:1806.00280[cond-mat.supr-con] and P.A. Marchetti, F. Ye , Z.B. Su and L. Yu, submitted

P-Th-2: Ab initio studies on superconductivity and inhomogeneity in Hg-based cuprate superconductor T. Ohgoe1, M. Hirayama2, T. Misawa3, K. Ido3, Y. Yamaji4, and M. Imada1,5

1Research Institute for Science and Engineering, Waseda University, 2RIKEN Center for Emergent Matter Science, 3Institute for Solid State Physics, The University of Tokyo. 4Department of Applied Physics, The University of Tokyo, 5Toyota Physical and Chemical Research Institute

Despite many experimental and theoretical studies on high-Tc cuprates, understanding its rich physics remains one of the most important outstanding problems in materials science. In this work [1], we studied an ab initio effective Hamiltonian of a high-Tc Hg-based cuprate superconductor [2] by cutting-edge numerical methods. We reproduced experiments including superconducting phase and its competition with a period-4 charge ordered state near the hole density ~0.1. Crucial role of realistic off-site interactions on the amplitude and stability of superconductivity is revealed. Furthermore, we find that the enhancement of superconductivity is correlated with that of charge fluctuations rather than spin fluctuations. These achievements are the essential steps towards solving the long-standing problem on the mechanism of high-Tc superconductivity as well as its competition with charge orders. [1] T. Ohgoe, M. Hirayama, T. Misawa, Y. Yamaji, K. Ido, and M. Imada, arXiv:1902.00122. [2] M. Hirayama, T. Misawa, T. Ohgoe, Y. Yamaji, and M. Imada, arXiv:1901.00763.

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P-Th-3: Exotic electronic structure of a multilayer cuprate superconductor revealed by a laser-ARPES.

S. Kunisada1, S. Isono2, Y. Kohama1, S. Sakai3, C. Bareille1, S. Adachi4, S. Sakuragi1,

R. Noguchi1, K. Kurokawa1, R. Sekine2, K. Kuroda1, T. Kim5, C. Cacho5, T. Tohyama6,

S. Shin1, K. Tokiwa2, T. Kondo1

1ISSP, the University of Tokyo, Kashiwa, Chiba 277-0882, Japan 2Dept. of applied electronics Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan 3RIKEN CEMS, Wako 351-0198, Japan 4MANA NIMS, Tsukuba 305-0044, Japan 5Diamond light source, Harwell Campus, Didcot OX11 0QX, UK 6Dept. of applied physics Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan The high-Tc copper oxide superconductor (cuprate) can drastically change its phase diagram with increasing the number of CuO2 layers per unit cell. In three or more layers of cuprates, the inner layer is surrounded and protected by the outer layer. It has been suggested from NMR studies that an ideal CuO2 layer is formed on inner layer with a flat, uniform distribution of in-plane carriers, without being affected by disorder caused by carrier doping from the outer dopant layers [1]. Moreover, cuprate with more CuO2 layers have stronger interlayer magnetic coupling. Therefore, it is suggested that antiferromagnetism is developed in the multilayers cuprate [1]. We focus on 5 layers cuprate, Ba2Ca4Cu5O10(Fy,O1-y)2 to study the exotic electric state in protected inner CuO2 plane by angle-resolved photoelectron spectroscopy and quantum oscillation measurements. We will discuss the detailed results in poster presentation.

[1] H. Mukuda et al., J. Phys. Soc. Jpn. 81 (2012) 011008.

P-Th-4: Analysis of k-space electronic structure of Bi2Si2Ca2Cu3O10+� cuprate superconductor Z. Q. Hao1, C. W. Zou1, X. T. Li1, H. W. Li1, Y. Ji1, M. Xu1 and Y. Y. Wang1,2 1State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China 2Collaborative Innovation Center of Quantum Matter, Beijing 100084, China The trilayer cuprate Bi2Si2Ca2Cu3O10+δ (Bi-2223) with three CuO2 planes exhibits the highest superconducting Tc = 110K in the Bi2Sr2Can-1CunO(2n+4)+δ (n=1,2,3) family. The electronic structure of dispersive Bogoliubov quasiparticle excitations is one of the key elements revealing the higher Tc property. Here we use scanning tunneling microscopy and spectroscopy surveying the low-energy electronic structure of Bi-2223 both in real space and momentum space (k-space). By analyzing Bogoliubov quasiparticle interference (QPI) pattern, the dispersion and underlying Fermi surface are determined. Our result shows that the Bogoliubov quasiparticle exists in a larger energy scale compared to its bilayer cousin. Moreover, the interference pattern exhibits more detailed structure than mere QPI peaks in octet model, which is more consistent to the case that interference is caused by smooth form of disorder [1]. These findings may shed new light on the nature of superconductivity in cuprates. [1] M. A. Sulangi, M. P. Allan and J. Zaanen, Phys. Rev. B 96. 134507 (2017).

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P-Th-5: Quantized Massive Gauge Fields, Pseudogaps, and Anomalous Angle-resolved Photoemission Spectra in High-Tc Cuprates I. Kanazawa, R. Maeda, T. Orihara Department of Physics, Tokyo Gakugei University , Tokyo184-8501, Japan Angle-resolved photoemission spectroscopy(ARPES) has played an important role in Developing understanding of high-Tc cuprates [1]. The present authors [2,3] have introduced quantized collective-massive gauge fields around the doped holes as collective modes, which contain effects of spin fluctuation, charge fluctuation, and phonons, and suggested strongly that the quantized massive gauge fields are mediating Cooper pairing in high-Tc cuprates. In this study, we have argued the anomalous spectra of ARPES of high-Tc cuprates, using quantized massive gauge fields, from the field-theoretical point of view. [1] T. Yoshida et al. J.Phys.Soc.Jpn.81,011006(2012) [2] I. Kanazawa, R. Maeda, J.Suipercond.Nov.Magn.30,49(2017) [3] I. Kanazawa, R. Maeda, J.Siupercond.Nov.Magn.31,671(2018)

P-Th-6: Appearance of a novel collective spin excitation in cuprate superconductors due to Rashba spin-orbit interaction and spin-twisting itinerant motion of electrons H. Koizumi1 and D. Manabe2 1Center for Computational Sciences, U. of Tsukuba, Tsukuba, 305-8577, Japan 2Graduate School of Pure and Applied Sciences, U. of Tsukuba, Tsukuba, 305-8577, Japan Superconductivity in cuprates exhibits remarkable deviations from that in standard superconductors whose Tc and electronic excitations are explained by the BCS theory. Tc at optimal doping corresponds to the stabilization temperature of nano-sized loop currents, and the magnetic excitation spectrum shows an hourglass-shaped dispersion that seems to indicate the presence of spin-vortices [1]. We have been theoretically showing that the spin-vortices and nano-sized loop currents arise naturally in the doped Mott insulator due to the realization of spin-twisting itinerant motion of electrons, which is stabilized by the Rashba spin-orbit interaction. We also argued that this stabilization explains the magnetic field enhanced charge-order, the dome-shaped hole-doping dependence of Tc, and the persistent generation [2]. Here, we report another Rashba interaction effect; the appearance of a novel collective spin excitation due to the Rashba interaction. [1] R. Hidekata and H. Koizumi, J. Supercond. Nov. Magn. 24, 2253 (2011). [2] D. Manabe and H. Koizumi, J. Supercond. Nov. Magn. https://doi.org/10.1007/s10948-018-4977-0

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P-Th-7: Electronic structure of underdoped triple-layer cuprate Bi2Sr2Ca2Cu3O10+d S. Ideta1, S. Adachi3, N. Sasaki3, S. Yamaguchi3, T. Watanabe3 and K. Tanaka1,2 1 National Institutes of Natural Science, Institute for Molecular Science, Okazaki, Japan 2 The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Japan 3 Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori, Japan To understand the mechanism of high-Tc superconductivity in cuprates is a crucial issue and the energy gap seen in the superconducting (SC) and normal states is believed to be an important piece of evidence for the non-BCS behavior of the SC transition for the underdoped regime in the high-Tc cuprate superconductors. Triple-layer Bi-based cuprate superconductor,

Bi2Sr2Ca2Cu3O10+d (Bi2223), which shows the highest Tc (= 110 K) among the Bi-based cuprates, has two inequivalent CuO2 planes with different hole carrier and the corresponding two energy bands were directly observed by angle-resolved photoemission spectroscopy (ARPES) [1,2]. In this study, we have investigated the momentum dependence of energy gaps in the underdoped (UD) Bi2223 (Tc = 80 K) by ARPES. We found an as-yet-unknown energy gap with a node in the normal state. The underlying electronic structure in UD Bi2223 to keep high Tc is different from the double- and single-layer cuprates and sheds light on the mechanism of high-Tc cuprate superconductivity. [1] S. Ideta et al., Phys. Rev. Lett. 104, 227001 (2010). [2] S. Ideta et al., Phys. Rev. B 85, 104515 (2012).

P-Th-8: Pseudogap in the c-axis (interplane) conductivity of a pair of t-J planes with a single doped hole P. Adamus1, D. Munzar1 1Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 2, 61137 Brno, Czech Republic We report on results of our study of the c-axis (interplane) optical conductivity of a pair of weakly coupled copper oxygen planes with a single doped hole. The planes are described using the t-J model and approximations of the well known spin polaron approach [1] are employed. The polaron problem is solved using a simple variational technique, on the subspace where the hole is dressed by a single spin excitation. The calculated dispersion relation is roughly consistent with that of the selfconsistent Born approximation. The variational ansatz allows us to analyze the optical transitions, to evaluate the corresponding matrix elements and to estimate the temperature dependence of the conductivity. The conductivity diplays a pseudogap opening with decreasing temperature associated with a spectral weight shift from low energies to a band arround ~ 2J. Our results provide a qualitative explanation for the trends in the data of underdoped cuprates [2]. [1] G. Martinez, P. Horsch, Phys. Rev. B 44, 317 (1991). [2] Li Yu et al., Phys. Rev. Lett 100, 177004 (2008).

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P-Th-9: Normal and anomalous self-energies of the high-Tc cuprates Bi2Sr2CaCu2O8+d revealed by ARPES T. Yoshida1, D. Ootsuki1, K. Yamawaki1, D. Shimonaka1, D. Shibata1, H. Eisaki2, T. Sasagawa3, A. Fujimori4, H. Kumigashira5, K. Ono5, M. Arita6, H. Namatame6, M. Taniguchi6, S. Ideta7, K. Tanaka7 1Graduate School of Human and Environmental Studies, Kyoto University, 2National Institute of Advanced Industrial Scienceand Technology (AIST), 3Materials and Structures Laboratory, Tokyo institute of Technology, 4Department of Physics, University of Tokyo, 5Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), 6Hiroshima Synchrotron Radiation Center, Hiroshima University, 7UVSOR Facility, Institute for Molecular Science A recent ARPES study have reported the self-energy for the spectra with superconducting gap [1] and pointed out the existence of bosonic mode in the self-energy, while the origin of the

mode is unclear at present. We have performed ARPES study of Bi2Sr2CaCu2O8+d and have extracted the self-energy from the spectra. Particularly, we have separated the normal and anomalous self-energy in the anti-nodal spectra. While the both self-energies have a characteristic energy, the energy scale does not appear in the spectra, consistent with the theoretical results of the hidden fermion model [2,3].

[1] J. M. Bok et al., Sci. Adv. 2, e1501329 (2016). [2] S. Sakai, M. Civelli, and M. Imada, Phys. Rev. Lett. 116, 057003 (2016). [3] Y. Yamaji, T. Yoshida, A. Fujimori, M. Imada, arXiv:1903.08060.

P-Th-10: Mixed lanthanide based superconductor Sm1-xLnxFeAs O0.75F0.25 (Ln= Ce and La) Moumita Naskar1, Ratnamala Chatterjee1 and Ashok Kumar Ganguli2 1Department of Physics, Indian Institute of Technology, New Delhi 110016, India. 2Department of Chemistry, Indian Institute of Technology, New Delhi 110016, India. Iron pnictides are a new family of high temperature superconductors, where the iron-pnictogen layers play an important role to induce superconductivity [1]. As a consequence, chemical substitution along with carrier-doping or chemical pressure on the crystal system can drastically modify its electrical properties including the superconducting transition temperature (Tc) [2]. Effect of rare earth substitution in 1111 iron oxipnictide SmFeAsO0.75F0.25 has been studied. Polycrystalline Sm1-xCexFeAsO0.75F0.25 and Sm1-xLaxFeAsO0.75F0.25 (x= 0, 0.25, 0.5, 0.75, 1) have been successfully synthesized by conventional solid state reaction method. Temperature dependent field cooled (FC) and zero field cooled (ZFC) magnetization study shows systematic variation in Tc from 53 K to 33 K for Ce-doped and from 53 K to 22 K for La-doped compositions. Larger ionic radii of both Ce and La affect the inner chemical pressure on Fe-As bond which leads to change in Tc. [1] Yoichi Kamihara,Takumi Watanabe, Masahiro Hirano and Hideo Hosono, J. Am. Chem. Soc 130, 3296 (2008). [2] A.K. Ganguli, J. Prakash, S.J. Singh, and S. Patnaik, Eur. Phys. J. B 73, 177 (2010).

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P-Th-11: Q dependence of the resonance mode on iron-based superconductor Fe(Te0.5Se0.5) M. Ishikado1, K. Kodama2, R. Kajimoto3, M. Nakamura3, Y. Inamura3, K. Ikeuchi1, S. Ji1, M. Arai3, and S. Shamoto4 1Neutron Science and Technology Center, CROSS, Tokai, 319-1106, Japan 2Materials Sciences Research Center, JAEA, Tokai, Ibaraki 319-1195, Japan 3J-PARC Center, JAEA, Tokai, Ibaraki 319-1195, Japan 4Advanced Science Research Center, JAEA, Tokai, Ibaraki 319-1195, Japan Spin fluctuations and Orbital fluctuations are considered to be mechanisms of iron-based

superconductors, and the superconducting symmetry of these become s and s++ wave,

respectively. Inelastic neutron scattering measurements have been performed on a superconducting single crystal FeTe0.5Se0.5, to examine the Q-dependent enhancement of the

dynamical structure factor, S(Q,E), from Q=(0, 0) to (p, 0), and (p, p) in the superconducting state. Constant-E cuts of S(Q,E) suggest that the enhancement is not uniform in the magnetic

excitation, and limited around Q=(p, 0). This result is consistent with the theoretical simulation of the magnetic resonance mode due to the BCS coherence factor with sign-reversing order

parameter of s -wave [1].

[1] Y. Nagai and K. Kuroki, Phys. Rev. B 85, 134521 (2012).

P-Th-12: Theoretical prediction of anitiferro nematic order above TS in BaFe2As2 S. Onari and H. Kontani Department of Physics, Nagoya University, Furo-cho, Nagoya 464-8602, Japan The origin and nature of rich nematic symmetry breaking phenomena are the central issues in Fe-based superconductors. We explained that the origin of the structural phase transition is the ferro orbital order by using the Aslamazov-Larkin vertex correction (AL-VC) theory [1]. In BaFe2As2, however, nematicity starts to develop at T=T *[2], which is higher than the structural phase transition temperature TS. The origin of the nematicity at T * is a long standing unsolved problem. Both the extrinsic origin due to the local uniaxial strain and the intrinsic origin due to another phase transition have been proposed. In addition, the pseudogap in the density of states is observed below T *[3]. In this study, we predict that the origin of the nematicity below T * is the antiferro charge nematic order by solving the CDW equation [4] based on the AL-VC theory [1]. The T-liner

behavior of nxz-nyz below T * and the emergence of pseudogap are naturally explained by the antiferro charge nematic order. The variety of nematicity in Fe-based superconductors is understood by the AL-VC theory. The antiferro charge nematic fluctuation would favor the S++ wave superconductivity without sign reversal. [1] S. Onari and H. Kontani, Phys. Rev. Lett. 109, 137001 (2012). [2] S. Kasahara et al., Nature 486, 382 (2012). [3] T. Shimojima et al., Phys. Rev. B 89, 045101 (2014). [4] S. Onari, Y. Yamakawa, and H. Kontani, Phys. Rev. Lett. 116, 227001 (2016).

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P-Th-13: Comparison of Te and S substitution in FeSe thin films F. Nabeshima1, T. Ishikawa1, N. Shikama1, S. Nakamura1, H. Kurokawa1 and A. Maeda1 1Dept. of Basic Science, the University of Tokyo, Tokyo 153-8902, Japan We grew single crystalline films of FeSe1-xSx with x ≤ 0.43 via pulsed laser deposition. As x increases, the structural transition temperature decreases and the superconducting transition temperature, Tc, shows a gradual decrease even when the structural transition disappears. We observed a new kink structure in the resistivity-temperature curves for films with large x, which is likely due to a magnetic transition. The obtained phase diagram of FeSe1-xSx is similar to that of bulk FeSe1-xSx except for the possible magnetic transition, but is in contrast to that of FeSe1-

yTey films, which shows a sudden increase of Tc at the composition where the structural transition disappears[1]. These results demonstrate that the relationship between the nematicity and the superconductivity is not universal in FeSe[2]. A magneto-transport study revealed a positive correlation between carrier densities and Tc in these films. These results suggest that the structural transition affects the electronic structure differently between Fe(Se,S) and Fe(Se,Te) and that this is the direct cause of the difference in the Tc behaviors at the end point of the structural transition. [1] Y. Imai et al., Sci. Rep. 7, 46653 (2017). [2] F. Nabeshima et al., J. Phys. Soc. Jpn. 87, 073704 (2018). P-Th-14: Manifestation of the multiband nature in the BCS-BEC crossover of FeSe1-xSx T. Hashimoto1, Y. Ota1, A. Tsuzuki1, T. Nagashima1, A. Fukushima1, S. Kasahara2,

Y. Matsuda2, K. Matsuura3, Y. Mizukami3, T. Shibauchi3, K. Okazak , S. Shin1

1Institute for Solid State Physics (ISSP), University of Tokyo, Chiba 277-8581, Japan 2Department of Physics, Kyoto University, Kyoto 606-8502, Japan 3Department of Advanced Materials Science, University of Tokyo, Chiba 277-8561, Japan Weak coupling Bardeen-Cooper-Schrieffer (BCS) pairing and strong coupling Bose-Einstein condensation (BEC) are connected continuously through a crossover regime [1]. The iron-based superconductor FeSe is suggested to be in the BCS-BEC crossover regime [2]. We explore the BCS-BEC crossover in the isovalent substituted system, FeSe1-xSx, by using laser-excited angle-resolved photoemission spectroscopy. We find a systematic change of the

curvature of a hole band around the G point in the Brillouin zone, and observed a pseudogap at x = 0.21 above Tc. These are the evidence that FeSe1-xSx can be controlled from a BCS region

to a BEC region by increasing x. The estimated value of D/eF, a conventional measure for “coupling strength”, behaves contrary to the single-band calculation. This demonstrates the importance of the multiband nature for the BCS-BEC crossover in FeSe1-xSx. [1] M. Randeria et al., Annu. Rev. Cond. Matt. Phys. 5, 209-232 (2014). [2] S. Kasahara et al., Proc. Natl. Acad. Sci. USA 111, 16309-16313 (2014).

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P-Th-15: Manifestations of impurity induced s±→s₊₊ transition in ferropnictides O. V. Dolgov1,2, D.V. Efremov3, A.A. Golubov4

1Donostia International Physics Center, San Sebastian, Spain 2P.N. Lebedev Physical Institute, RAS, Moscow, Russia 3 IFW Dresden, Helmholtzstrasse 20, Dresden, Germany 4 Faculty of Science and Technology, University of Twente, Enschede, The Netherlands We investigate effects of disorder on the density of states, the single particle response function and optical conductivity in multiband superconductors with s± symmetry of the order parameter, where s±→s₊₊ transition may take place [1]. In vicinity of the transition the superconductive gapless regime is realized. It manifests itself in anomalies in the above mentioned properties. As a result, intrinsically phase-insensitive experimental methods like ARPES, tunneling and terahertz spectroscopy [2] may be used for revealing of information about the underlying order parameter symmetry. [1] D.V. Efremov, A.A. Golubov, O.V. Dolgov, New J. Phys, 15, 013002 (2013) [2] M. B. Schilling, A. Baumgartner, B. Gorshunov, E. S. Zhukova, V. A. Dravin, K. V. Mitsen, D. V. Efremov, O. V. Dolgov, K. Iida, M. Dressel, and S. Zapf, Phys. Rev. B 93, 174515 (2016)

P-Th-16: Sm-substitution Effects on Transport properties in BiS2 based superconductor La1-ySmyO0.5F0.5BiS2 N. Momono, T. Suda, Y. Wang, T. Tamura, S. Takeyabu, K. Nara, F. Ogura, Y. Shibayama Applied Physics Course, Muroran Institute of Technology, Muroran 050-8585, Japan We report the transport properties of BiS2 based layered superconductor La1-ySmyO0.5F0.5BiS2 (y=0.1-0.7). The electrical resistivity and Hall coefficient for y=0.3 and 0.4 show upturns below T*~130 and 200 K, respectively. Temperature dependence of Seebeck coefficients for y=0.3 and 0.4 change slopes around T*, suggesting the reduction of the density of states (DOS) at the Fermi level EF. The resistivity and Hall coefficient for y>0.5, where superconducting transition temperature Tc is enhanced, show a metallic behavior. These results suggest that the superconductivity for y=0.3 and 0.4 is suppressed to some extent by the reduction of DOS at EF, which will be associated with some kind of charge-density-wave. [1] S. Iwasaki et al., J. Phys. Soc. Jpn. 88, 041005 (2019).

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P-Th-17: Topological classification of superconducting nodes on rotational axes Shuntaro Sumita1, Takuya Nomoto2, Ken Shiozaki3, and Youichi Yanase1 1Department of Physics, Kyoto University, Kyoto 606-8502, Japan 2Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan 3Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502, Japan Recent development in exact classification of a superconducting gap has elucidated various unconventional nodal structures [1-4], which have not been predicted by the classification of order parameter based on the point group [5]. One important previous result is that all symmetry-protected line nodes are characterized by topological indices [3]. Another intriguing discovery is the gap structures depending on the angular momentum jz of electrons on threefold and sixfold rotational-symmetric lines [4]. Stimulated by these findings, we classify all crystal symmetry-protected nodes on n-fold (n = 2, 3, 4, and 6) axes, by using the combination of group theory and K theory. As a result, it is shown that the classification by group theory completely corresponds with the topological classification. Based on the obtained results, we discuss gap structures in several candidate superconductors. [1] T. Micklitz and M. R. Norman, Phys. Rev. B 80, 100506 (2009). [2] T. Nomoto and H. Ikeda, J. Phys. Soc. Jpn. 86, 023703 (2017). [3] S. Kobayashi, S. Sumita, Y. Yanase, and M. Sato, Phys. Rev. B 97, 180504 (2018). [4] S. Sumita and Y. Yanase, Phys. Rev. B 97, 134512 (2018). [5] M. Sigrist and K. Ueda, Rev. Mod. Phys. 63, 239 (1991).

P-Th-18: Inversion-breaking structural distortion driven by strong spin-orbit coupling in Cd2Re2O7 Hishiro T. Hirose,1 Taichi Terashima,1 Daigorou Hirai,2 Yasuhito Matsubayashi,2 Naoki Kikugawa,1 David Graf,3 Kaori Sugii,2 Shiori Sugiura,1 Zenji Hiroi,2 and Shinya Uji1 1National Institute for Materials Science, Tsukuba 305-0003, Japan 2Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-0882, Japan 3National High Magnetic Field Laboratory, Florida State University, Tallahassee 32310, USA We have investigated the Fermi surface of a pyrochlore oxide superconductor Cd2Re2O7. It undergoes a structural transition at 200 K, which breaks the inversion symmetry [1]. The transition is theoretically considered as an odd-parity multipolar order of the electron states induced by strong spin-orbit coupling [2]. It lifts the spin degeneracy of electronic bands and splits the Fermi surface via the antisymmetric spin-orbit coupling. Our quantum oscillation measurements [3] have revealed that the hole Fermi surface for one spin species almost disappears. This fact leads to the consequence that the spin splitting of the hole band provides large energy gain at the transition, and corroborates the scenario that the instability of the electron states due to strong spin-orbit coupling drives the inversion-breaking order. [1] Z. Hiroi et al., J. Phys. Soc. Jpn. 87, 024702 (2018). [2] L. Fu, Phys. Rev. Lett. 115, 026401 (2015). [3] Y. Matsubayashi et al., J. Phys. Soc. Jpn. 87, 053702 (2018).

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P-Th-19: Topological superconductor in quasi-one-dimensional Tl2−xMo6Se6 S. M. Huang1, C. H. Hsu2,3, S. Y. Xu4, C. C. Lee5, S. Y. Shiau2,3, H. Lin2,3,6, and A. Bansil7

1Department of Physics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan 2Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, 6 Science Drive 2, Singapore 117546, Singapore 3Department of Physics, National University of Singapore, 2 Science Drive 3, Singapore 117542, Singapore 4Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA 5Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan 6Institute of Physics, Academia Sinica, Nankang Taipei 11529, Taiwan 7Department of Physics, Northeastern University, Boston, Massachusetts 02115, USA

Quasi-one-dimensional molybdenum selenide compound Tl2−xMo6Se6 has a nodal surface protected by the screw axis without spin-orbit coupling (SOC) and a cubic Dirac node with SOC. We propose that the compound is a topological superconductor when intersublattice attraction is dominant. The doping effect from Tl-deficient (0≤x≤0.1) does not show noticeable change to superconductivity. At weak SOC, the superconductor prefers the triplet d vector lying perpendicular to the chain direction and two-dimensional E2u symmetry, which is driven to a nematic order by spontaneous rotation symmetry breaking. Majorana fermions will show on the (001) surface, especially at the tricrystal point of three nematic domain walls, which is served as a time-reversal-invariant vortex core.

[1] S. M. Huang, C. H. Hsu, S. Y. Xu, C. C. Lee, S. Y. Shiau, H. Lin, and A. Bansil, Phys. Rev. B 98, 97, 014510 (2018).

P-Th-20: Quasi-particle evidence for the nematic state above Tc in SrxBi2Se3 Y. Sun1,2, S. Kittaka2, T. Sakakibara2, K. Machida3, J. H Wang4, J. S. Wen4, X. Z. Xing5, Z. X. Shi5 and T. Tamegai6

1Dept. of Phys. and Math., Aoyama Gakuin University, Sagamihara 252-5258, Japan 2ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan 3Department of Physics, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan 4Department of Physics, Nanjing University, Nanjing 210093, China 5School of Physics, Southeast University, Nanjing 211189, China 6Department of Applied Physics, University of Tokyo, Hongo, Tokyo 113-8656, Japan In the electronic nematic state, an electronic system has a lower symmetry than the crystal structure of the same system. Electronic nematic states have been observed in various unconventional superconductors such as cuprate- and iron-based, heavy-fermion, and topological superconductors. The relation between nematicity and superconductivity is a major unsolved problem in condensed matter physics. By angle-resolved specific heat measurements, we report bulk quasi-particle evidence of nematicity in the topological superconductor SrxBi2Se3. The specific heat exhibited a clear 2-fold symmetry despite the 3-fold symmetric lattice. Most importantly, the 2-fold symmetry appeared in the normal state above the superconducting transition temperature. This is explained by the angle-dependent Zeeman effect due to the anisotropic density of states in the nematic phase. Such results highlight the interrelation between nematicity and unconventional superconductivity.

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P-Th-21: Wannier pairs in the superconducting twisted bilayer graphene and related systems S. Ray1, J. Jung2, and T. Das1 1Department of Physics, Indian Institute of Science, Bangalore -560012, India 2Department of Physics, University of Seoul, Seoul 02504, Korea The twisted bilayer graphene (TBG) presents a new setting where superconductivity emerges on the flat bands whoseWannier wavefunctions spread over many graphene unit cells, forming the so-called Moir´e pattern. To unravel how Wannier states form Cooper pairs, we study the interplay between electronic, structural, and pairing instabilities in TBG. For comparisons, we also study graphene on boron-nitride (GBN) possessing a different Moir´e pattern, and single-layer graphene (SLG) without a Moir´e pattern. We compute the pairing eigenvalues and eigenfunctions by solving a linearized superconducting gap equation, where the spin-fluctuation mediated pairing potential is evaluated from materials specific tight-binding band structures. We find an extended s-wave as the leading pairing symmetry in TBG. In contrast, GBN assumes a p + ip-wave and SLG has the d + id-wave symmetry. Moreover, while p + ip, and d+id pairings are chiral, and nodeless, but the extended s-wave channel possesses accidental nodes. [1] S. Ray, J. Jung, and T. Das, Wannier pairs in the superconducting twisted bilayer graphene and related systems, arXiv:1804.09674.

P-Th-22: Infrared activation of Higgs mode in superconducting NbN by supercurrent injection S. Nakamura1, Y. Iida2, Y. Murotani2, R. Matsunaga3, H. Terai4, and R. Shimano1,2 1Cryogenic Research Center, University of Tokyo, Yayoi, Tokyo 113-0032, Japan 2Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan 3The Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan 4National Institute of Information and Communications Technology, Iwaoka, Kobe 651-2492, Japan Higgs mode in superconductors is an amplitude oscillation of the order parameter, which is charge neutral and spinless and thus is typically not coupled to the electromagnetic field. Here we demonstrate that, in the presence of dc supercurrent, the Higgs mode becomes infrared active and is directly observed in the linear optical conductivity measurement [1]. We observed a sharp resonance peak at the superconducting gap energy (ω = 2∆) in the optical conductivity spectrum of thin NbN films with supercurrent injection over a wide temperature range below the critical temperature. The peak shows a reasonable agreement with the recent theoretical prediction [2]. This method opens a new pathway to study the Higgs mode in a wide variety of superconductors. [1] S. Nakamura et al., arXiv:1809.10335 (2018). [2] A. Moor, A. F. Volkov, and K. B. Efetov, Phys. Rev. Lett. 118, 047001 (2017).

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P-Th-23: Chiral Spin Density Wave and d+id Superconductivity in the Magic-Angle-Twisted Bilayer Graphene Cheng-Cheng Liu1, Li-Da Zhang1, Wei-Qiang Chen2, and Fan Yang1 1School of Physics, Beijing Institute of Technology, Beijing 100081, China 2Shenzhen Institute for Quantum Science and Engineering and Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China We investigate the recently discovered correlated insulating state and superconductivity in the magic angle twisted bilayer graphene with a two orbital model on the superstructure honeycomb lattice [1]. A van Hove singularity and Fermi-surface (FS) nesting are found in the doping levels relevant to the correlated insulator and unconventional superconductivity revealed experimentally. We identify the two phases as weak-coupling FS instabilities and performed random-phase-approximation based calculations to study the electron instabilities. As a result, we find chiral d+id topological superconductivity bordering the correlated insulating state near half-filling, which is identified as noncoplanar chiral spin-density wave ordered state. The phase diagram obtained in our approach is qualitatively consistent with experiments.

[1] Cheng-Cheng Liu, Li-Da Zhang, Wei-Qiang Chen, and Fan Yang��Phys. Rev. Lett. 121,

217001 (2018)

P-Th-24: Observation of topological surface states in superconducting TaSe3 C. Lin1, R. Noguchi1, K. Kuroda1, P. Zhang1, J. Xu1, K. Yaji1, S. Shin1, A. Nomura2, M. Sakoda3, M. Tsubota4, S. Tanda3, and T. Kondo1 1Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan 2Department of Physics, Tokyo University of Science, Tokyo, 162-0825, Japan 3Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan 4Department of Physics, Gakushuin University, Tokyo 171-0031, Japan The layered quasi-1D trichalcogenide TaSe3 shows no charge density waves differently from its analogues TaS3 and NbSe3, but superconductivity at ultra-low temperatures [1,2]. The first-principle calculations indicate that TaSe3 actually belongs to a strong topological insulator (TI) phase, and moreover predict intriguing strain effects of tunable topological phase transitions among strong TI, weak TI, Dirac semimetal, and normal insulator phases [2]. To verify the topological properties of TaSe3, we have performed spin- and angle-resolved photoemission spectroscopy measurements to directly probe topological surface states (TSSs) and the spin polarization. On top of the qualitative agreement between the band structure observed and the calculation, an anomalous temperature evolution of TSSs has also been detected, the details of which will be discussed in the poster presentation. [1] A. Nomura et al., EPL. 119, 17005 (2017) [2] S. Nie et al., Phys. Rev. B. 98, 125143 (2018)

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P-Th-25: Time-resolved ARPES study on Ta2NiSe5 T. Suzuki1, Y. Shinohara2, Y. Lu3, M. Watanabe1, J. Xu1, H. Takagi3,4, M. Nohara5, N. Katayama6, H. Sawa6, M. Fujisawa1, T. Kanai1, N. Ishii1, J. Itatani1, T. Mizokawa7, K. L. Ishikawa2, K. Okazaki1, and S. Shin1 1ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan. 2School of Engineering, University of Tokyo, Hongo, Tokyo 113-0033, Japan. 3Department of Physics, University of Tokyo, Hongo, Tokyo 113-0033, Japan. 4Max Planck Institute for Solid State Research, Heisenbergstrsse 1, 70569 Stuttgart, Germany. 5Research Institute for Interdisciplinary Science, Okayama University, Okayama, 700-8530, Japan. 6Department of Applied Physics, Nagoya University, Nagoya 464-8603, Japan. 7School of Advanced Science and Engineering, Waseda University, Shinjuku, Tokyo 169-8555, Japan. Ta2NiSe5 has been long proposed as an excitonic insulator based on the remarkable band flattening below 328 K due to the strong Coulomb attractive interaction between the conduction and valence bands. Recently, superconductivity was found to occur in Ta2NiSe5 under high pressure, which strongly suggests that Ta2NiSe5 possesses rich physics by stimuli. In this work, we intensively studied photo-excited non-equilibrium behavior by using time-resolved ARPES. We have discovered that it shows an insulator-to-metal transition [1], and successfully unveiled its precise mechanism by developing Fourier-domain ARPES.

[1] K. Okazaki, et al. Nature Commun. 9, 4322 (2018).

P-Th-26: Observation of high-Tc superconductivity in a Ca2RuO4

nanocrystal H. Nobukane1,2, K. Yanagihara1, Y. Kunisada3, Y. Ogasawara1, K. Isono1, K. Nomura1, K. Tanahashi3, T. Nomura3, T. Akiyama2,3 and S. Tanda2,4 1Department of Physics, Hokkaido University, Sapporo 060-0810, Japan 2Center of Education and Research for Topological Science and Technology, Hokkaido University, Sapporo 060-8628, Japan 3Center for Advanced Research of Energy and Materials, Hokkaido University, Sapporo 060-8628, Japan 4Department of Applied Physics, Hokkaido University, Sapporo 060-8628, Japan By reducing the thickness of a layered crystal to a nanometer level, a nanofilm leads to novel quantum states that have not previously been found in bulk crystals. Here we report the realization of high-temperature superconductivity in Ca2RuO4 nanofilm single crystals. A Ca2RuO4 thin film exhibits zero resistance and typical Berezinskii-Kosterlitz-Thouless transition behavior where the highest onset temperature 96 K is observed in electric transport measurements. We also found that the induced bias current and the tuned film thickness cause a superconductor-insulator transition. Our results demonstrate the presence of two-dimensional high-Tc superconductivity in Ca2RuO4 nanofilm. The fabrication of nanofilms made of layered material enables us to discuss rich superconducting phenomena in ruthenates. [1] H. Nobukane et al., arXiv:1703.09459

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P-Th-27: Tuning the magnetocrystalline anisotropy in RCoPO by means of R substitution: a ferromagnetic resonance study G. Prando1, A. Alfonsov,2 A. Pal,3 V. P. S. Awana,3 B. Büchner,2 V. Kataev2 1Department of Physics, University of Pavia, 27100 Pavia, Italy 2Leibniz-Institut für Festkörper- und Werkstoffforschung Dresden, Dresden, Germany 3Department of Physics, Indian Institute of Sciences, 560012 Bangalore, India 4National Physical Laboratory, New Delhi, India We report on broad-band electron-spin resonance measurements performed within the itinerant ferromagnetic phase of RCoPO (R = La, Pr, Nd, and Sm) [1]. We reveal that the R substitution is highly effective in gradually introducing a sizable easy-plane magnetocrystalline anisotropy within the Co sublattice. We explain our results in terms of a subtle interplay of structural effects [2,3] and of indirect interactions between the f and d orbitals from R and Co, respectively. Our observations provide interesting information on the crucial role of R ions in affecting the electronic properties of the CoP layers, of possible interest also for the isostructural FeAs-based family of high-Tc superconductors. [1] G. Prando et al., Phys. Rev. B 94, 024412 (2016). [2] G. Prando et al., Phys. Rev. B 87, 064401 (2013). [3] G. Prando et al., Phys. Rev. B 92, 144414 (2015).

P-Th-28: Ultra high-pressure magnetization measurement for Kitaev-candidate honeycomb materials Y. Tsuyuki1, Y. Hayashi1 K. Kitagawa1, K. Whiteaker1, M. Blankenhorn2, and H. Takagi1, 2

1Department of Physics, University of Tokyo, Hongo 7-3-1, Tokyo 113-0033, Japan 2Max Planck Institute, Stuttgart, Heisenbergstrasse, Stuttgart 1, 70569, Germany Kitaev honeycomb model is an exceptional spin liquid because of exact solution by introducing Majorana fermions. However, the Kitaev model needs bond-dependent interaction between 1/2 spins [1]. Last year, it is theoretically suggested that Kitaev interaction emerges for honeycomb 4f1 systems. Na2PrO3 has an effective magnetic moment

0.99 µB and shows a negative Curie-Weiss temperature qCW = -15 K [3]. The calculation suggested that AF Kitaev interaction is more pronounced if a Pr-O-Pr length is shortened by exchange from Na to Li [4]. However, Li2PrO3 does not crystallize in a honeycomb lattice. Thus, our purpose is to observe 4f1 Kitaev physics by enhancing AF Kitaev interaction in Na2PrO3 through pressurizing. Based on a high-pressure cell invented by N. Tateiwa et al [5], we developed a new cell by minimizing a background and explored high-pressure phase diagram of Na2PrO3. It is found that a glassy AF phase tends to disappear by increasing pressure. To pursuit a possible liquid ground state, we plan to conduct high-pressure NMR with a high-quality single-crystal Na2PrO3. [1] A. Kitaev, Ann. Phys. (N. Y.) 321, 2 (2006). [3] Y. Hinatsu, Y. Doi Journal of Alloys and Compounds 418 (2006) 155-160. [4] S.Jang, et al, e-print arXiv:cond-mat.str-el/1807.01443 (2018). [5] N. Tateiwa et al., Rev. Sci. Instrum. 82, 053906 (2011).

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P-Th-29: Multipole fluctuation mechanism for fully gapped s-wave SC in CeCu2Si2 R. Tazai, and H. Kontani Department of physics, Nagoya University, Furo-cho, Nagoya 464-8602, Japan

For a long time, CeCu2Si2 has been believed as typical d-wave superconductor. However, recent experiments have revealed that s-wave SC without sign reversal is realized in CeCu2Si2. This fact cannot be explained by conventional spin fluctuation theories.

In this study, we analyze J=5/2 periodic Anderson model considering higher-order many body effects given by Aslamasov-Larkin type vertex correction (AL-VC) [1,2]. AL-VC corresponds to the interference between electric and magnetic multipole fluctuations. Due to the AL-VC for susceptibilities, electric quadrupole and hexadecapole fluctuations strongly develop while the magnetic ones remain small. Using obtained multipole fluctuations, we solve the linearized gap equation. Considering the AL-VC for the gap equation beyond Migdal-Eliashberg formalism, attractive pairing interaction due to hexadecapole fluctuations are strongly enhanced. Therefore, s-wave SC is realized even in the heavy fermion system. Furthermore, we find that Tc for s-wave SC can be enhanced by introducing small electron-phonon interaction belongs to A1g symmetry. The present multipole fluctuation mechanism will be applicable to various interesting heavy fermion superconductor.

[1] R. Tazai and H. Kontani, ArXiv:1902.10968 (2019).

[2] R. Tazai and H. Kontani, Phys. Rev. B 98, 205107 (2018).

P-Th-30: ARPES study of heavy-fermion uranium superconductors S. Fujimori1, I. Kawasaki1, Y. Takeda1, T. Okane1, Y. Saitoh1, A. Fujimori1,2, H. Yamagami1,3, Y. Haga4, E. Yamamoto4, and, Y. Ōnuki 5 1Materials Sciences Research Center, Japan Atomic Energy Agency, Hyogo 679-5148, Japan 2Department of Applied Physics, Waseda University, Tokyo 169-8555, Japan 3Department of Physics, Kyoto Sangyo University, Kyoto 603-8555, Japan 4Advanced Science Research Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan 4Faculty of Science, University of the Ryukyus, Okinawa 903-0213, Japan Some heavy-fermion uranium compounds exhibit unconventional superconductivity. One of their characteristics is that the superconductivity often coexists with a magnetic ordering. In particular, the coexistence of the ferromagnetic ordering and superconductivity have been found only in uranium compounds. We have studied the electronic structures of heavy-fermion uranium superconductors by the ARPES with the soft X-ray from SPring-8 [1]. Recently, we have further developed the three-dimensional (3D) ARPES method, in which all three parameters in ARPES experiments (two detecting angles of photoelectrons and incident photon energy) are scanned, and the complete volume electronic structure of the entire Brillouin zone can be obtained. The result of some heavy Fermion superconductors will be presented.

[1] S. Fujimori et al., J. Phys. Soc. Jpn. 85, 062001 (2016).

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P-Th-31: Effects of nonmagnetic impurity scattering on nonlinear terahertz response by Higgs and Leggett modes Y. Murotani1, and R. Shimano1,2 1Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan 2Cryogenic Research Center, The University of Tokyo, Tokyo 113-0032, Japan Multiband superconductors are a fascinating platform to explore non-equilibrium phenomena because they can accommodate multiple collective modes. Recently, it has been theoretically predicted that nonmagnetic impurity scattering significantly enhances the nonlinear terahertz response of the Higgs mode, a collective mode of the amplitude of the order parameter [1]. However, its effect on the Leggett mode, a collective mode of the phase difference of order parameters, has not been elucidated. To clarify contributions from these collective modes, we theoretically examined nonlinear terahertz response of dirty superconductors by a density matrix method which gives realistic optical conductivity [2]. We found that nonlinear excitation of the Leggett mode is not enhanced even when dipole-allowed virtual states are induced by nonmagnetic impurity scattering. As a result, both the light-induced oscillation of the superconducting gaps and the resulting third-harmonic generation are dominated by the Higgs mode for irradiation of an intense terahertz electromagnetic wave.

[1] T. Jujo, J. Phys. Soc. Jpn. 87, 024704 (2018). [2] Y. Murotani, and R. Shimano, arXiv: 1902.01104.

P-Th-32: Emergences of ferromagnetic fluctuations and d+ip-wave SC due to the Andreev bound state at the edge of d-wave superconductors S. Matsubara and H. Kontani Department of Physics, Nagoya University, Nagoya 464-8602, Japan In the square lattice Hubbard models, we found in Ref. [1] that ferromagnetic (FM) fluctuations develop in the normal state at the (1,1) edge, due to the edge induced Friedel oscillation. In this study, we reveal that the FM fluctuations further increase just below the transition temperature of the bulk d-wave SC (Tc

bulk), due to the formation of the Andreev bound state (ABS) at the (1,1) edge. Furthermore, the enhanced edge FM fluctuations induce the edge d+ip-wave SC. Here, we analyze the (1,1) edge models corresponding to YBa2Cu3O7-x in the bulk d-wave SC state. We calculate the site-dependent spin susceptibility by using the random phase approximation (RPA) and the fluctuation exchange (FLEX) approximation formulated in the real space. As the temperature decreases, just below Tc

bulk, the FM fluctuations begin to develop at the (1,1) edge more drastically due to the edge induced ABS of the bulk d-wave SC. Next, we study the edge triplet SC mediated by the FM fluctuations by analyzing the linearized edge gap equation in the presence of the finite bulk d-wave gap. Just below Tc

bulk, the eigenvalue of the edge p-wave state increases sharply as the temperature decreases and exceeds unity at Tc

edge≲Tcbulk. This means that

the edge p-wave SC is caused by the bulk d-wave SC through the enhancement of the FM fluctuations. The phase difference between the d-wave gap and the p-wave gap is π/2 in the real space. It is the edge d+ip-wave SC. The d+ip-wave SC state is time reversal invariant but the parity is broken, and therefore the spin current flows along the (1,1) edge. [1] S. Matsubara, Y. Yamakawa and H. Kontani, J. Phys. Soc. Jpn, 87, 073705 (2018).

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P-Th-33: Nature of superconducting fluctuation in photo-excited systems R. Iwazaki1, N. Tsuji2 and S. Hoshino1

1Department of Physics, Saitama University, Shimo-Okubo, Saitama 338-8570, Japan

2RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan

By using pump-probe spectroscopy, the light-induced superconductivity (SC) have been

proposed in 2D systems [1,2] and in the 3D material K3C60 [3] above the transition temperature. As for the theoretical researches, it has been discussed that the induced photons cause the change in the effective interaction among electrons through the change in phonons by lights, and also the direct effect to the electronic systems. In this study, we investigate the SC fluctuation effects in photo-excited systems above the transition temperature by using time dependent Ginzburg-Landau theory with a simple setup. We have revealed that the SC fluctuation and photo-induced current decay with power-law or logarithmic functions [4]. This power-law/logarithmic decay is a characteristic feature of critical phenomena but is observed in a photo-excited situation away from the critical point. In the presentation, we will discuss the physical quantities such as current and paraconductivity as functions of time and pump-light amplitude. [1] D. Fausti, et al., Science 331(6014), 189-191 (2011). [2] S. Kaiser, et al., Phys. Rev. B 89, 184516 (2014). [3] M. Mitrano, et al., Nature 530, 461-464 (2016). [4] R. Iwazaki, N. Tsuji and S. Hoshino, arXiv:1904.05820 (2019).

P-Th-34: Magnetic Excitations in Magnetization Plateau Phases in Frustrated Two-Leg Spin Ladder T. Sugimoto, K. Sasaki, and T. Tohyama Department of Applied Physics, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan Frustrated spin ladders have attracted much attention due to magnetization plateaus by spontaneously breaking of translational symmetry at low temperatures. For example, a frustrated two-leg spin ladder exhibits three magnetization plateaus as ground states with one-third, one-half, and two-third magnetization normalized by saturated magnetization [1]. Here we investigate dynamical properties in these magnetization plateau phases. Dynamical density-matrix renormalization group study indicates a vestige of spontaneously broken translational symmetry even in excitation spectra. In particular, we show that a quasi-particle picture defined by an extended unit cell well explains a low-energy excitation. Thus, this result implies an exotic particle caused by spontaneously broken symmetry, such like the Goldstone and Higgs modes [2]. [1] T. Sugimoto, M. Mori, T. Tohyama, and S. Maekawa, Phys. Rev. B 97, 144424 (2018). [2] K. Sasaki, T. Sugimoto, T. Tohyama, in preparation.

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P-Th-35: Topological Transition in Hard-Core Bosonic Haldane Model

Takuya Susa, Takanori Sugimoto, and Takami Tohyama

Department of Applied Physics, Tokyo University of Science. The topological Haldane model on two-dimensional honeycomb lattice is well known as the first example where it can exhibit quantum Hall effect without magnetic fields [1]. Interestingly, the recent study has shown that the bosonic systems exhibit non-trivial topological number [2].

Here, we consider a hard-core boson instead of fermion and boson as a quantum object on the Haldane model. The Jordan-Wigner transform of one-half spin to fermion causes the many-body interaction in two-dimensional systems. Therefore, we can clarify not only the quantum statistical effects but also the effects of interaction on the topological state in this model. To break the time-reversal symmetry, we introduce a second-neighbor hopping term with a phase depending on number operator at the neighboring sites, which corresponds to the scalar chirality of three spins. Additionally, we also introduce an anisotropy in the lattice to break the sublattice symmetry. As the result, we have found the signature of topological transition in this model. Our study also indicates a possibility of new topological states in quantum spin systems.

References [1] F. D. M. Haldane, Phys. Rev. Lett. 61, 18 (1988). [2] H. Kondo, Y. Akagi, and H. Katsura, Phys. Rev. B 99, 041110(R) (2019)

P-Th-36: A “BCS light” on Vortex Cores in a high Tc Superconductor Ivan Maggio-Aprile1,Tim Gazdic1,Christophe Berthod1, Andreas Erb2,and Christoph Renner1

1 Université de Genève-DQMP, 24 quai Ernest Ansermet, Geneva, Switzerland 2 Walther Meissner Institut für Tieftemperaturforschung, Garching, Germany Scanning tunnelling spectroscopy (STS) suggests that vortex cores of high-Tc superconductors (HTCS) do not match with BCS expectations. Bi-based HTCS vortices reveal a pseudogap-like quasiparticle DOS, while cores of YBa2Cu3O7−δ (Y123) exhibits electron-hole symmetric states at finite subgap energy [1]. The missing zero-bias anomaly raised many questions about the BCS nature of the cores in these compounds. In recent STS experiments on Y123, we found that the subgap states are not a specific signature of the vortices, but belong to an electronic background uniformly measured across the surface [2]. In our analysis, the total tunnelling current is the combination of two channels: one associated with the quasiparticle excitations of a d-wave superconductor, and the other corresponding to a non-superconducting background. Comparing our data with a Bogoliubov-de Gennes model, we demonstrate that the vortex cores in HTCS present the expected BCS quasiparticle LDOS [3]. The model provides further insight into the vortex-core structure, which is different for each vortex due to an irregular lattice and depends on the Fermi surface topology more than on the gap symmetry. [1] I. Maggio-Aprile et al., Phys. Rev. Lett. 75, 2754 (1995) [2] J. Bruer et al., Nat. Commun. 7, 11139 (2016) [3] C. Berthod et al., Phys. Rev. Lett. 119, 237001 (2017)

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P-Th-37: Photoinduced superconductivity by η pairs in a Mott insulator S. Miyakoshi1, T. Kaneko2, T. Shirakawa3,4, and S. Yunoki1,3,4 1RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan 2Department of Physics, Columbia University, New York, New York 10027, USA, 3Computational Materials Science Research Team, RIKEN Center for Computational Science (R-CCS), Kobe, Hyogo 650-0047, Japan, 4Computational Condensed Matter Physics Laboratory, RIKEN Cluster for Pioneering Research (CPR), Wako, Saitama 351-0198, Japan

The recent discovery of photoinduced transient superconducting behaviors in some high-Tc cuprates in pulse irradiation experiments urges a further understanding of nonequilibrium dynamics in strongly correlated electron systems. Here, we theoretically investigate the pulse irradiation on the Hubbard model by employing unbiased numerical methods. We find that unconventional superconducting correlations are photoinduced even in the Mott insulator of the Hubbard model [1]. The superconductivity found here is due to the η-paring mechanism, characterized by the staggered pair-density-wave oscillations in the off-diagonal long-range correlation, and is absent in the ground-state phase diagram. We also discuss the photoinduced η pairs in a charge transfer insulator and the possible extension of the η-paring mechanism to other systems with different lattice geometry and several types of interactions. [1] T. Kaneko, T. Shirakawa, S. Sorella, and S. Yunoki, Phys. Rev. Lett. 122, 077002 (2019).

P-Th-38: Drumhead surface states and their signatures in quasiparticle scattering interference M. Biderang1, A. Leonhardt2, A. Schnyder2, A. Akbari1,

1Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, Korea 2Max Planck Institute for Solid State Research, Heisenbergstraße 1, D-70569 Stuttgart, Germany We consider a two-orbital tight-binding model defined on a layered three-dimensional hexagonal lattice to investigate the properties of topological nodal lines and their associated drumhead surface states. We examine these surface states in centrosymmetric systems, where the bulk nodal lines are of Dirac type (i.e., fourfold degenerate), as well as in noncentrosymmetric systems with strong Rashba and/or Dresselhaus spin-orbit coupling, where the bulk nodal lines are of Weyl type (i.e., twofold degenerate). We find that in noncentrosymmetric systems the nodal lines and their corresponding drumhead surface states are fully spin polarized due to spin-orbit coupling. We show that unique signatures of the topologically nontrivial drumhead surface states can be measured by means of quasiparticle scattering interference, which we compute for both Dirac and Weyl nodal line semimetals. [1] M. Biderang et la., Phys. Rev. B 98, 075115 (2018)

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P-Th-39: A New Generation of ARPES Spectrometers for Direct Band Structure Observation M. Weidner1, M. Wietstruk1, and A. Thissen1 1SPECS Surface Nano Analysis GmbH, Berlin, Germany Knowledge of the electronic band structure is a fundamental piece of information in the research and development of novel functional materials such as 2D-materials, topological insulators or superconductors. The only experimental method for a more or less direct observation of the band structure is angle resolved photoemission spectroscopy (ARPES). While ARPES has been around as a reliable source of information for decades, the respective spectrometers have recently taken a quantum leap in functionality and ease of use due to novel concepts in electron lens systems and more powerful data processing capabilities, massively cutting down the required time of effort of band structure observation and therefore increasing material screening capability. In this contribution, we will introduce and discuss the latest developments in ARPES spectrometers such as the momentum microscope, recent advances in time of flight spectrometers and angle-shifting lenses and their implications for users from the field of superconductor research.