program - zhejiang universityzimp.zju.edu.cn/~xinwan/workshops/sgw13/sgw20131012.pdfsino-german...

Sino-German (International) Workshop

On Kondo and Mott Physics in Correlated Matter

PROGRAM

October 13-17, 2013 Zhejiang University, Hangzhou

Sponsored by

Sino-German Center for Research Promotion

Zhejiang University

Max Planck Institute for Chemical Physics of Solids

Table of Contents

Sino-German (International) Workshop…………………...…………...…………...1-2

Program Overview…………………. ………………………………………...............3

Attendee Guide…………………………. ………………………………………........4

Map of Zijingang Campus, Zhejiang University………………………………….......5

Map of Hangzhou City…………………. ………………………………………........6

Workshop Program…………………. ………………………………………….....7-11

Abstracts of Talks………………………. ……………………………………….12-58

Abstracts of Posters……………………. ………………………………………..59-74

List of Participants………………………. ………………………………………75-83

Sino-German (International) Workshop

On Kondo and Mott Physics in Correlated Matter October 13-17, 2013

Scope

In recent years, intensive efforts have been devoted to revealing emergent quantum phases and

quantum phase transitions in correlated matter. Continuous quantum phase transitions, known as

quantum critical points (QCPs), are considered to provide a unifying principle for a large variety

of phenomena, including unconventional forms of superconductivity and magnetisms,

metal-insulator transitions and non-Fermi liquid behavior. Likewise, competing interactions that

cannot be simultaneously satisfied are known to give rise to emergent quantum phases such as

spin liquids in antiferromagnets with frustrated interactions.

In April, 2012, we organized the first Sino-German bilateral workshop on emergent phases in

correlated and topological matter (http://zimp.zju.edu.cn/~xinwan/workshops/SGW12/), which

was in parallel with the 2012 Hangzhou workshop on quantum matter

(http://zimp.zju.edu.cn/~iccqm/workshop2012/). The joint workshop covered subjects of

unconventional superconductivity in general, quantum phase transitions and topological phases.

This year, the workshop will mainly concentrate on the exotic quantum states/phenomena

associated with the Kondo effect and Mott physics in correlated materials, with special emphasis

on heavy fermion systems. One of our purposes is to bring together a group of distinguished

experts working on these topics so that they can update each other on the newest developments in

these fields and seek for mutual cooperation, which will certainly help reveal the above-mentioned

problems.

Topics

The major theme of the workshop is on “Kondo and Mott Physics in Correlated Matter”. Within

this theme, the workshop will focus on the following topics:

1) Heavy fermion physics, which includes Kondo lattice behavior, unconventional

superconductivity, competing orders and topological Kondo insulators.

2) Quantum phase transitions in correlated materials, focusing on the universality of

quantum critical points, together with the recent developments in multiferroics and

systems with strong spin-orbit coupling.

3) Metal-insulator transitions, mainly of the Mott type.

4) Exotic ground states in strongly frustrated magnets.

5) Kondo physics in nanoscale and hetero-structures.

Co-Chairs

Frank Steglich (Max Planck Institute for Chemical Physics of Solids)

Huiqiu Yuan (Zhejiang University)

1

Local Organizing Committee

Xin Lu (Zhejiang University)

Fan-Long Ning (Zhejiang University)

Xin Wan (Zhejiang University)

Zhu-an Xu (Zhejiang University)

Fu-Chun Zhang (The University of Hong Kong/Zhejiang University)

About Sponsors

The workshop is financially supported by the Sino-German Center for Research Promotion

(Website: http://www.sinogermanscience.org.cn), the Center for Correlated Matter and the

Department of Physics at Zhejiang University and Max-Planck-Institute for Chemical Physics of

Solids.

Venue

Mengminwei Building 139, Zijingang Campus, Zhejiang University, Hangzhou

Website

http://zimp.zju.edu.cn/~xinwan/workshops/SGW13/index.php

2

Time Oct. 13th Oct. 14th Oct. 15th Oct. 16th Oct. 17th

Welcome Speech

(Chair: Fu-Chun Zhang)

08:20-08:30 Frank Steglich

Topological Kondo Insulators

(Chair: Fu-Chun Zhang) Mott Physics I

( Chair: Hilbert v Löhneysen) Heavy-Fermion I

( Chair: Zachary Fisk) Kondo Lattice

(Chair: Qimiao Si)

08:30-09:00 Zachary Fisk Kazushi Kanoda Jochen Wosnitza Guang-Ming Zhang

09:00-09:30 Xian-Hui Chen Frank Steglich Tuson Park Jian-Hui Dai

09:30-10:00 Steffen Wirth Hui-Qiu Yuan Xin Lu Yi-Feng Yang

10:00-10:30 Tea Break (Poster Session)

Correlated Electrons I

(Chair: Tao Xiang) Topological Aspects

(Chair: Xian-hui Chen) Correlated electrons II (Chair: Yuji Matsuda)

Mott Physics II (Chair: Alois Loidl)

10:30-11:00 Yu-Peng Wang Claudia Felser Nan-Lin Wang Michael Lang

11:00-11:30 Liu Hao Tjeng Qiang-Hua Wang Malte Grosche Jens Müller

11:30-12:00

Fu-Chun Zhang Xi Dai Chang-Qing Jin Yi Zhou

12:00-13:30 Lunch Break

High Tc Cuprates

(Chair: Roser Valenti) Spin Frustrations/Liquid

(Chair: Hai-Hu Wen) Heavy Fermion II

(Chair: Laura Greene)

13:30-14:00 Tao Xiang Alois Loidl Michael Nicklas

14:00-14:30 Thilo Kopp Roser Valenti Pei-Jie Sun

14:30-15:00 Zheng-Yu Weng Shi-Yan Li Oliver Stockert

15:00-15:30 Edmund Gerstner Stefan Kirchner Tea Break (Poster Session)

15:30-16:00 Tea Break (Poster Session) Spectroscopy

(Chair: Steffen Wirth)

Iron Pnictides

(Chair: Nan-Lin Wang) Quantum Criticality

(Chair: Michael Lang) Wei Bao

16:00-16:30 Hai-Hu Wen Hilbert v Löhneysen Xing-Jiang Zhou

16:30-17:00 Laura Greene Cornelius Krellner Concluding Remarks

17:00-17:30 Jian-Lin Luo Qimiao Si

17:30-18:00

Registration at

Qizhen Hotel

Yuan Li Yuji Matsuda

Excursion

18:00-19:30 Reception Dinner Banquet Dinner

Program Overview VENUE: Mengmingwei Building 139, Zijingang Campus

3

Attendee Guide

About Board and Lodging

Please note that the invited speakers are accommodated at Qizhen Hotel.

Date Time Location

Oct. 13th Reception 18:00-19:30 F2, Qizhen Hotel

Buffet Lunch 12:00-13:30 F1, Qizhen Hotel Oct. 14th

Dinner 18:00-19:30 F3, Cafeteria




Banquet 18:00-19:30 Zhiweiguan (besides the West Lake)



About the Excursion

Two local trips will be organized for the invited speakers. The details of the tours are as

follows:

Time of Trips: 13:30-17:30, October 16, 2013 (Wed.)

Tour A: The West Lake, to go around the lake and to take a boat to the islands in the

middle of the lake. (See Hangzhou Travel Guide, page 16)

Tour B: Lingyin Temple and Peak Flying from Afar, to visit the temple and the famous

Buddha statues. (See Hangzhou Travel Guide, page 24)

Conference Contact Info

Ying Li (Secretary) Mobile: 13958119681 Email: [email protected]

Hui-Qiu Yuan (Prof.) Mobile: 15925666127 Email: [email protected]

Hotel Contact Info

Qizhen Hotel（园正·启真酒店）

Tel.: 86-571-88982888

Add.: 866 Yuhangtang Road, Hangzhou (Inside Zijingang Campus, Zhejiang University)

Maps

Please find both the maps of the campus and the city (where the university and the hotel

located).

4

Map of Zijingang Campus, Zhejiang University

5

Map of Hangzhou City

6

Workshop Program

Date Time Program

10/14 Welcome Speech (Chair: Fu-Chun Zhang)

08:20-08:30 Frank Steglich

Topological Kondo Insulators (Chair: Fu-Chun Zhang)

08:30-09:00 Zachary Fisk (University of California, Irvine, USA)

SmB6: A Topological Insulator?

09:00-09:30 Xian-Hui Chen (University of Science and Technology of China, PRC)

Angular Dependent Magnetoresistance Evidence for Robust Surface State in Kondo

Insulator SmB6

09:30-10:00 Steffen Wirth (MPI-CPfS, Germany)

STM on Strongly Correlated Electron Systems: from Metals to Insulators

10:00-10:30 Tea break; Group photo

Correlated Electrons I (Chair: Tao Xiang)

10:30-11:00 Yu-Peng Wang (Institute of Physics, CAS, China)

Off-diagonal Bethe Ansatz and Solutions of Integrable Models without U(1) Symmetry

11:00-11:30 Liu Hao Tjeng (MPI-CPfS, Germany)

High Temperature Phases of Strongly Correlated Oxides

11:30-12:00 Fu-Chun Zhang (The University of Hong Kong, China)

Localization and Conductance Quantization in Si-doped 2-Dimesnional Topological

Insulator

12:00-13:30 Lunch break

High Tc Cuprates (Chair: Roser Valenti)

13:30-14:00 Tao Xiang (Institute of Physics, CAS, China)

Tensor Renormalization of Quantum Spin Liquid States using Projected Entangled Simplex

States

14:00-14:30 Thilo Kopp (University of Augsburg, Germany)

The Complexity of Cuprate Grain Boundaries

14:30-15:00 Zheng-Yu Weng (Tsinghua University, China)

7

Date Time Program

Mott Physics, Sign Structure, and High-Temperature Superconductivity

15:00-15:30 Edmund Gerstner (Nature Publishing Group)

How to get published in Nature (and its sister journals)

15:30-16:00 Tea break (Poster Session)

Iron Pnictides (Chair: Nan-Lin Wang)

16:00-16:30 Hai-Hu Wen (Nanjing University, China)

Pairing Induced by Magnetic Interactions in Iron Pnictide Superconductors Revealed by

Scanning Tunneling Spectroscopy

16:30-17:00 Laura H. Greene (University of Illinois at Urbana-Champaign, USA)

Detecting Strong Electron Correlations with Quasiparticle Scattering Spectroscopy: Electron

Matter in Fe-pnictides, Fe-chalcogenides, and Heavy Fermions

17:00-17:30 Jian-Lin Luo (Institute of Physics, CAS, China)

Multi-phase Transitions in Pnictide Ce12Fe57.5As41

17:30-18:00 Yuan Li (Peking University, China)

Longitudinal Spin Excitations and Magnetic Anisotropy in Antiferromagnetically Ordered

BaFe2As2

18:00-19:30 Dinner

10/15 Mott Physics I ( Chair: Hilbert v Löhneysen)

08:00-09:00 Kazushi Kanoda (University of Tokyo, Japan)

Mott Physics in 2D Organics: AF/spin Liquid, Quantum Criticality, Pseudo-gap and

Superconductivity

09:00-09:30 Frank Steglich (MPI-CPfS, Germany)

Mott Physics in a Kondo Lattice

09:30-10:00 Hui-Qiu Yuan (Zhejiang University, China)

Field-induced Localized-itinerant Transition in CeRhIn5


Topological Aspects (Chair: Xian-hui Chen)

10:30-11:00 Claudia Felser (MPI-CPfS, Germany)

Heusler Compounds, Spin Orbit coupling, Topological Insulators and New Effects

8

Date Time Program

11:00-11:30 Qiang-Hua Wang (Nanjing University, China)

Dominant Triplet Pairing and Possible Weak Topological Superconductivity in BiS2-based

Superconductors

11:30-12:00 Xi Dai (Institute of Physics, CAS, China)

Topological Phases in Mix Valence Compounds


Spin Frustrations/Liquid (Chair: Hai-hu Wen)

13:30-14:00 Alois Loidl (University of Augsburg, Germany)

Spin-Orbital Physics in Frustrated Lattices

14:00-14:30 Roser Valenti (Goethe-University, Frankfurt am Main, Germany)

Correlation Effects in Frustrated Systems: Triangular and Honeycomb Lattices

14:30-15:00 Shi-Yan Li (Fudan University, China)

Possible Spin Liquid State on a Honeycomb Lattice

15:00-15:30 Stefan Kirchner (MPI for the Physics of Complex Systems, Germany)

On the Dual Fermion Approach to Charge Order, Spin Frustration, and Transport


Quantum Criticality (Chair: Michael Lang)

16:00-16:30 Hilbert v. Löhneysen (KIT, Germany)

Routes to Quantum Criticality in Heavy-fermion Systems

16:30-17:00 Cornelius Krellner (Goethe-University, Frankfurt am Main, Germany)

Exploring Quantum Criticality by Applying Chemical Pressure

17:00-17:30 Qimiao Si (Rice University, USA)

Electronic Correlations and Quantum Criticality in Iron Pnictides

17:30-18:00 Yuji Matsuda (Kyoto University, Japan)

Quantum Critical Point Hidden beneath the Superconducting Dome in Iron-pnictides

18:00-19:30 Dinner

10/16 Heavy-Fermion I ( Chair: Zachary Fisk)

08:30-09:00 Jochen Wosnitza (HMD, Dresden, Germany)

9

Date Time Program

Aspects of Fermiology in Correlated Metals

09:00-09:30 Tuson Park (Sungkyunkwan University, Korea)

Impurity in the Quantum Critical Superconductor CeCoIn5

09:30-10:00 Xin Lu (Zhejiang University, China)

Exploring the Heavy-fermion Superconductor CeIrIn5 under Pressure


Correlated electrons II (Chair: Yuji Matsuda)

10:30-11:00 Nan-Lin Wang (Institute of Physics, CAS, China)

Revealing Multiple Density Wave Orders in Non-superconducting Titanium Oxypnictide

Na2Ti2As2O

11:00-11:30 Malte Grosche (University of Cambridge, UK)

Correlated States near Magnetic and Structural Quantum Phase Transitions

11:30-12:00 Chang-Qing Jin (Institute of Physics, CAS, China)

Effects of Pressure on Certain Correlated Electron System


13:30-17:30 Excursion

18:00-19:30 Banquet

10/17 Kondo Lattice (Chair: Qimiao Si)

08:30-09:00 Guang-Ming Zhang (Tsinghua University, China)

Weak Ferromagnetism with the Kondo Screening Effect in the Kondo Lattice Systems

09:00-09:30 Jian-Hui Dai (Hangzhou Normal University, China)

From Dirac Fermion to Dirac Heavy Fermion: Emergent Semi-metallic Heavy Fermion

Phase on a Honeycomb Lattice

09:30-10:00 Yi-Feng Yang (Institute of Physics, CAS, China)

Heavy Electron Kondo Liquid and Long-range Orders


10

Date Time Program

Mott Physics II (Chair: Alois Loidl)

10:30-11:00 Michael Lang (University of Frankfurt, Germany)

Field-induced Berezinskii-Kosterlitz-Thouless Scenario in a 2-Dimensional Spin-dimer

System

11:00-11:30 Jens Mueller (Goethe-University, Frankfurt am Main, Germany)

Low-frequency Charge Carrier Dynamics at the Mott Transition in the Quasi-2D Organic

Conductors κ-(BEDT-TTF)2X

11:30-12:00 Yi Zhou (Zhejiang University, China)

Quantum Spin Liquids at the Vicinity of Mott Transition


Heavy Fermion II (Chair: Laura Greene)

13:30-14:00 Michael Nicklas (MPI-CPfS, Germany)

Non-Fermi Liquid and Exotic Heavy-fermion Behavior in the Filled Skutterudites XPt4Ge12

(X=Ce, Sm)

14:00-14:30 Pei-Jie Sun (Institute of Physics, CAS, China)

Local Kondo Scattering Detected by Nernst Effect

14:30-15:00 Oliver Stockert (MPI-CPfS, Germany)

Competing Magnetic Phases in Yb(Rh1-xCox)2Si2


Spectroscopy (Chair: Steffen Wirth)

15:30-16:00 Wei Bao (Renming University, China)

Vacancy Order and Magnetic Excitations in the 245 Fe-based Superconductors

16:00-16:30 Xing-Jiang Zhou (Institute of Physics, CAS, China)

Insulator-Metal-Superconductor Transitions in Cuprate Superconductors and Iron-Based

Superconductors

16:30-17:00 Concluding Remarks

11

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12

SmB6: A Topological Insulator?

Zachary Fisk

University of California, Irvine, USA

The Kondo insulator SmB6 is theoretically predicted to be a topological insulator. We present evidence for a protected conducting surface state in this material, a signature characteristic of the topological insulator. We also discuss other known Kondo insulators in this context.

13

Angular Dependent Magnetoresistance Evidence for Robust Surface

State in Kondo Insulator SmB6

Xian-Hui Chen

University of Science and Technology of China, PRC

A long-standing puzzle in well-known Kondo insulator (KI) SmB6 is the low-temperature saturation in resistivity which was considered as the result of some ill-defined “in-gap” state. Very recently, there are accumulating evidences on that such “in-gap” state could be ascribed to novel topological surface state (TSS). So far, although some characteristics of TSS were revealed, the exact topological nature remains elusive. Here we gave unambiguous evidence on two-dimensional (2D) surface state in SmB6 single crystals by angular-dependent magnetoresistance(AMR), and demonstrated that it is robust against various surface modifications, suggesting its nontrivial topological nature. With nonmagnetic La3+ ions doping, the surface state is still measurable in AMR up to 20% doping level. Moreover, a remarkable surface-roughness tuned conductivity was also observed below 10 K in the same doping range. Both were ascribed to the result of a trivial surface conduction layer near crystal surface. Therefore, a two-channel model near the surface was needed to account for the low-temperature transport in SmB6. * In collaboration with F. Chen, C. Shang, A. F. Wang, X. G. Luo, T. Wu, and X. H. Chen.

14

STM on Strongly Correlated Electron Systems:

From Metals to Insulators

Steffen Wirth

Max Planck Institute for Chemical Physics of Solids Dresden, Germany

Hybridization is a fundamental concept in strongly correlated electron physics. In heavy fermion metals, it may result in the generation of low-energy scales that can give rise to quantum criticality and unconventional superconductivity. We discuss the effects of hybridization and of the Kondo interaction as probed by STS and focus on the heavy fermion system YbRh2Si2 and the intermediate valence insulator SmB6, and discuss similarities and differences.

The material YbRh2Si2 is of specific topical interest due to a quantum critical point which appears to result not only from an antiferromagnetic instability but also from a Kondo break-down of the heavy quasiparticles [1]. We present STM and STS studies at low temperature [2]. The tunneling conductance clearly reflects the hybridization of conduction and 4f electrons as well as the crystal field excitations. In addition, the evolution of the Kondo lattice at low temperatures is investigated: While the Kondo lattice starts forming already at the single-ion Kondo temperature it dominates the material properties only at much lower temperatures. These findings by STS are augmented by additional measurements [3, 4].

Hybridization also plays a decisive role in the low temperature properties of the intermediate valence system SmB6. The hybridization gap, inter-multiplet transitions and possible crystal field excitations are observed by STS. The temperature evolution of these spectra again points toward the Kondo effect being at play. STS conducted on non-reconstructed surfaces gave results in excellent agreement with expectations for a Fano resonance. The impact of the surface properties on the STS data is discussed, also in relation to the recent proposal of a topologically protected surface state in SmB6 [5].

* In collaboration with S. Ernst, Z. Fisk, C. Geibel, Tae-Hwan Jang, S. Kirchner, C. Krellner, S. Rößler, S. Seiro, F. Steglich, L. H. Tjeng and G. Zwicknagl. [1] S. Friedemann et al., Proc. Natl. Acad. Sci. USA 107 (2010) 14547. [2] S. Ernst et al., Nature 474 (2011) 362. [3] H. Pfau et al., Phys. Rev. Lett. 110 (2013) 256403. [4] H. R. Naren et al., New J. Phys., accepted for publication. [5] M. Dzero et al., Phys. Rev. Lett. 104 (2010) 106408.

15

Off-diagonal Bethe Ansatz and Solutions of Integrable Models

without U(1) Symmetry

Yupeng Wang

Institute of Physics, Chinese Academy of Sciences, China

A systematic Bethe ansatz method will be introduced for the integrable models without U(1) symmetry, which can not be solved by the conventional Bethe ansatz methods because of the lack of a proper "local vacuum". By constructing the operator product identities of the transfer matrix, an extended T-Q relation, which could be universal for most integrable models, is observed. As examples, the exact solutions of some long standing problems such as the XXZ spin torus (related to the topological states of matter), the spin chains with arbitrary boundary fields (related to the Kondo or impurity problem in correlated hosts) and the XYZ model with odd number of sites are derived.

16

High Temperature Phases of Strongly Correlated Oxides

Liu Hao Tjeng,

Max Planck Institute for Chemical Physics of Solids, Dresden, Germany

Strongly correlated oxides show often quite spectacular and intriguing properties which can be traced back to the presence of several competing interactions leading to various forms of ordered phases at low temperatures. In order to unravel which of the interactions are relevant, we have set out to study the excitation spectra of several benchmark oxides as a function of temperature. By carrying out bulk sensitive hard-x-ray photoemission experiments from low to high temperatures, we can follow the changes in the spectra and thereby determine which and how local spin and orbital degrees of freedom as well as nearest neighbour spin-spin correlations influence the intricate and complex electronic structure of correlated oxides.

17

Localization and Conductance Quantization in Si-doped

2-Dimesnional Topological Insulator

Fu-Chun Zhang

The University of Hong Kong, China

Quantum spin Hall effect or 2-dimensional topological insulator were predicted theoretically and confirmed in experiments. However, the quantization of electric conductance has not been in high accuracy as in the quantum Hall effect until very recent data on Si-doped InAs/GaSb quantum well by Rui Du's group in Rice University. In this talk, we will discuss the effect of the localization to the quantization of the electric conductance. Our results are in good agreement with the experiment.

18

Tensor Renormalization of Quantum Spin Liquid States using

Projected Entangled Simplex States

Tao Xiang


We propose a new class of tensor-network states, which we name projected entangled simplex states (PESS), for studying the ground-state properties of quantum lattice models. These states extend the pair-correlation basis of projected entangled pair states (PEPS) to a simplex. PESS are an exact representation of the simplex solid states and provide an efficient trial wave function that satisfies the area law of entanglement entropy. We introduce a simple update method for evaluating the PESS wave function based on imaginary-time evolution and the higher-order singular-value decomposition of tensors. By applying this method to the spin-1/2 antiferromagnetic Heisenberg model on the kagome lattice, we obtain an accurate result for the ground-state energy, which sets the lowest upper bound yet achieved for this quantity.

19

The Complexity of Cuprate Grain Boundaries

Thilo Kopp

University of Augsburg, Germany

For twenty five years it has been known that the supercurrent through grain boundaries of cuprate superconductors depends exponentially on the misalignment angle between the adjacent crystallites of the grain boundary junction [a,b]. A microscopic understanding of this striking phenomenon is a key to control the maximum supercurrent achievable in wires and tapes of high temperature superconductors. We propose a solution to this longstanding problem which requires a multiscale approach to the full microscopic complexity of such grain boundaries. The buildup of charge inhomogeneities is identified as the dominant mechanism for the suppression of the supercurrent [c].

Strong correlations are known to severely reduce the mobility of charge carriers near half-filling and thus have an important influence on the current carrying properties of grain boundaries in cuprates. We apply a Gutzwiller method to investigate the critical current through microscopically reconstructed grain boundaries for a wide range of misalignment angles [d]. In good agreement with experimental data, we find a reduction of the current by one order of magnitude as compared to an analogous weak coupling evaluation. This reduction emerges from the interplay of charge fluctuations and strong correlations. Eventually, we analyze the formation of local magnetic moments at the grain boundaries [e].

a H. Hilgenkamp and J. Mannhart, Grain Boundaries in High-Tc Superconductors, Rev. Mod. Phys. 74, 485 (2002). b D. Dimos, P. Chaudhari, J. Mannhart, and F. K. LeGoues, Orientation Dependence of Grain-Boundary Critical Currents in YBa2Cu3O7−δ Bicrystals, Phys. Rev. Lett. 61, 219 (1988). c S. Graser, P. J. Hirschfeld, T. Kopp, R. Gutser, B. M. Andersen, and J. Mannhart, How Grain Boundaries Limit Supercurrents in High-Temperature Superconductors, Nature Phys. 6, 609 (2010). d F. A. Wolf, S. Graser, F. Loder, and T. Kopp, Supercurrent through Grain Boundaries of Cuprate Superconductors in the Presence of Strong Correlations, Phys. Rev. Lett. 108, 117002 (2012). e Iris Xhango, Magnetism and Transport at Grain Boundaries in Cuprates, Dissertation, University of Augsburg (2013).

20

Mott Physics, Sign Structure, and High-Temperature

Superconductivity

Zheng-Yu Weng

Institute for Advanced Study, Tsinghua University, China

Fermi sign structure of a Fermi gas will be fundamentally changed in the presence of strong interaction. We show that the new sign structure for the t-J model and Hubbard model can be precisely captured by a nonintegrable phase factor as reduced Fermion signs. The quantum interference due to such a sign structure is expected to dictate the novel behavior in (doped) Mott insulators. Utilizing DMRG numerical calculation, we demonstrate that a single hole doping into a Mott insulator is generally localized, thanks to the aforementioned destructive quantum interference, which is purely of strong correlation origin and isdifferent from the Anderson localization due to disorders. Important implications for delocalization/superconducting transition will be further discussed.

21

How to get published in Nature (and its sister journals)

Edmund Gerstner

Executive Editor, China, Nature Communications

So, you've discovered something extraordinary and you want to tell the world about it. Why would you publish it in a Nature journal? Which one should you choose? Indeed, why has Nature spawned so many new titles? What is Nature Communications, and what is it trying to do that other Nature journal don't do already? What is Open Access? In this talk I'll try to answer these and any other questions you have about getting published in a Nature journal. I'll also cover: what we look for in the papers that we consider for publication; the mechanics of how submissions are handled; how to decide if your paper could be for us; how to prepare a submission; and what to do when you think we (or our referees) have got a decision wrong. And, of course, what are we looking for in China?

22

Pairing Induced by Magnetic Interactions in Iron Pnictide

Superconductors Revealed by Scanning Tunneling Spectroscopy

Hai-Hu Wen

Nanjing University, China

Since the discovery of high temperature superconductivity in the iron pnictides and chalcogenides in early 2008, it remains unclear how the Cooper pairs are formed. There is a debate at this moment about whether the pairing is due to a retarded electron-boson interaction, as in the conventional phonon-mediated superconductors, although here the bosonic excitations may be the antiferromagnetic spin fluctuations. In this paper, we show the presence of the bosonic mode with the energy identical to that of the neutron resonance, and its close relationship with superconductivity in several iron based superconductors. It is found that in one single system, the mode is roughly related to the superconducting transition temperature in a linear way with a ratio of /Tc 4.3. The statistics on the vast data in one single sample indicate an anticorrelation between the mode energy and the superconducting gap, showing a resonance peak around /2 0.8. This dichotomy can be explained by the picture of spin fluctuation mediated superconductivity. Meanwhile we will show the clear evidence of the non-magnetic impurity induced in-gap states in iron pnictide superconductors, giving decisive evidence of the S pairing. In collaboration with: Huan Yang, Zhenyu Wang, Delong Fang and Lei Shan [1] Zhenyu Wang, et al., Nature Physics 9, 42-48(2013). [2] L. Shan, et al. Phys. Rev. Lett. 108, 227002 (2012). [3] Delong Fang et al., to be published. [4] Huan Yang et al., arXiv:1306.2001.

23

Detecting Strong Electron Correlations with Quasiparticle Scattering

Spectroscopy: Electron Matter in Fe-pnictides,

Fe-chalcogenides, and Heavy Fermions

Laura H. Greene

University of Illinois at Urbana-Champaign, USA

Quasiparticle scattering spectroscopy (QPS), also called point contact spectroscopy (PCS), a spectroscopic tool for detecting phonons, magnons, and single-impurity Kondo scattering, iswell established asa spectroscopic probe of the superconducting order parameter and its symmetry in conventional and unconventional superconductors. We have found this technique to besurprisingly sensitive tothe detection ofstrongelectron correlations in the “normal” (non-superconducting) stateof a variety of systems that exhibit the ubiquitous “domed” phase diagram. In four families of Fe pnictides and chalcogenides that other groups have shown to exhibit electronic nematicity as a stress-induced resistance anisotropyat temperatures above the structural phase transition (TSPT), we observe a dramatically-enhanced zero-bias QPS conductance, with an onset well above TSPT, and in Ba(Fe1-xCox)2As2 we identify a new region in the underdoped side of the phase diagram.1This is explained by an increased density of states at the Fermi level arising from orbital fluctuations.2This QPS conductance enhancement is not detected in compounds that do not exhibit such anisotropy above TSPT. In the heavy fermion URu2Si2 we detect the Fano resonance and hybridization gap as a distinct asymmetric double-peaked structure that opens as high as ~ 35 K.3All of our data indicate that QPS detectsa density of states arisingfrom electron correlations. 1. H. Z. Arham, et al.,Phys. Rev. B85, 214515; 1-4(2012). 2. Wei-Cheng Lee and Philip W. Phillips, Phys. Rev.B 86 245113; 1-5 (2012). 3. W.K. Park,et al.,Phys. Rev. Lett.108, 246403; 1-5 (2102); W.K Park, unpublished.

24

Multi-phase Transitions in Pnictide Ce12Fe57.5As41

Jian-Lin Luo


We have investigated the resistivity, susceptibility and specific heat of needle-shaped single crystalline Ce12Fe57.5As41. Multiple magnetic phase transitions have been observed. At higher temperatures, a ferromagnetic (FM) phase transition is observed with a Curie temperature of 100 K. At lower temperature around 50 K, an anti-ferromagnetic (AFM) transition is observed, and this AFM transition is easily suppressed by a magnetic field applied along b-axis. In addition, a logarithmic temperature dependence of resistivity above 100K is observed which may be related to Kondo scattering of localized d electron moments of Iron ions with conduction electrons. In comparison, we also studied the physical properties of La12Fe57.5As41

which show quite different behaviors to that of Ce12Fe57.5As41, indicating 4f electrons of Ce ions play an important role in the magnetic transitions. The origin of these magnetic transitions is discussed. In collaboration with: W. Wei, and X. D. Zhang.

25

Longitudinal Spin Excitations and Magnetic Anisotropy in

Antiferromagnetically Ordered BaFe2As2

Yuan Li

Peking University, China

We report on a spin-polarized inelastic neutron scattering study of BaFe2As2 in the antiferromagnetically ordered state. Three distinct excitation components are identified, with spins fluctuating along the c-axis, perpendicular to the ordering direction in the ab-plane, and parallel to the ordering direction. While the first two "transverse" components can be described by a linear spin-wave theory with magnetic anisotropy and inter-layer coupling, the third "longitudinal" component is generically incompatible with the local moment picture. It points towards a contribution of itinerant electrons to the magnetism already in the parent compound of this family of Fe-based superconductors.

26

Mott Physics in 2D Organics: AF/spin Liquid, Quantum Criticality,

Pseudo-gap and Superconductivity

Kazushi Kanoda

University of Tokyo, Japan

The layered organics, -(ET)2X, are well known as a family affording over-10-K superconductors. Recent experimental and theoretical studies show that this family are model systems for Mott physics in anisotropic triangular lattices, in which the electron correlation and the geometrical frustration are both controllable with pressure and/or substitution of anion, X. In this workshop, I review our recent experimental findings related to Mott physics, namely the antiferromagnetic-ordering/spin-liquid competition, quantum Mott criticality and pseudo-gap behavior appearing on the verge of Mott transition.

27

Mott Physics in a Kondo Lattice

Frank Steglich

MPI for Chemical Physics of Solids, Germany

The tetragonal compound YbRh2Si2 is a prototypical Kondo lattice system [1], which shows weak antiferromagnetic (AF) order below TN = 70 mK. A small critical magnetic field suffices to smoothly suppress the AF order at Bc ≈ 60 mT (c) [2]. As infered from magnetotransport [3, 4] and thermodynamic [5] measurements, Bc also denotes a “local”, i.e., Kondo destroying, quantum critical point (QCP) [6, 7] – frequently called a 4f – orbital selective Mott transition (at T = 0). The dynamical processes underlying the apparent break-up of the Kondo singlets in this material have been explored [8,9] by studying the Lorenz ratio L/L0 as a function of the control parameters temperature (T) and magnetic field (B). Here, L = ρ/w is the ratio of the electrical (ρ) and thermal (w = L0T/κ) resistivities, with κ being the thermal conductivity and L0 = (kB)2/3e2 Sommerfeld’s constant. By properly taking care of bosonic (magnon/paramagnon) contributions to the heat current which exist at finite temperature only, extrapolation of the measured data to T = 0 yields a purely electronic Lorenz ratio L/L0 = 1 at B ≠ Bc, i.e., inside the antiferromagnetically ordered and the paramagnetic phases. At B = Bc, we extrapolate L/L0 ≈ 0.9. Therefore, the Wiedemann Franz (WF) law holds at any value of the control parameter B, except for the field-induced QCP [8], as also illustrated by a pronounced heating of the sample when measuring the low – T electrical resistivity in the vicinity of the critical magnetic field [10]. Such a violation of the WF law has never been observed for any metal before; it is ascribed to scatterings of the electronic heat carriers from fermionic quantum-critical fluctuations, namely those of the Fermi surface. Work done in collaboration with H. Pfau, S. Hartmann, S. Lausberg, P. Sun, U. Stockert, M. Brando, S. Friedemann, C. Krellner, C. Geibel, S. Wirth, S. Kirchner, E. Abrahams and Q. Si [1] S. Ernst et al., Nature 474, 362 (2011). [2] J. Custers et al. Nature 424, 524 (2003). [3] S. Paschen et al., Nature 432, 881 (2004). [4] S. Friedemann et al., Proc. Natl. Acad. Sci. USA 107, 14547 (2010). [5] P. Gegenwart et al., Science 315, 969 (2007). [6] Q. Si et al., Nature 413, 804 (2001). [7] P. Coleman et al., J. Phys.: Condes. Matter 13, R 723 (2001). [8] H. Pfau et al., Nature 484, 493 (2012). [9] H. Pfau et al., Phys. Rev. Lett. 110, 256403 (2013). [10] S. Lausberg, Dissertation, TU Dresden (2013), unpublished.

28

Field-induced Localized-itinerant Transition in CeRhIn5

Hui-Qiu Yuan

Zhejiang University, China

In this talk, we will present our recent measurements of the specific heat, quantum oscillations and Hall resistivity up to a very high magnetic field (45T-75T) for the heavy fermion metal CeRhIn5. Upon applying a magnetic field, the antiferromagnetic (AFM) transition of CeRhIn5 is eventually suppressed to a quantum critical point around Bc=50T [1]. Both the quantum oscillations and the Hall resistivity consistently demonstrate clear evidence of a Fermi surface reconstruction at B*35T, i.e., inside the AFM state. Detailed analyses on the dHvA frequencies and the cyclotron masses suggest that the field-induced Fermi surface reconstruction at B* is accompanied by a localized-itinerant transition of 4f electrons in CeRhIn5, leading to a change of the Fermi surface from a small volume to a large one. Our experimental findings provide new insights to the theoretical understanding of quantum criticality in heavy fermions. This work is in collaboration with Lin Jiao, Tian Shang, Gui-ming Pang, E. D. Bauer, Yoshimitsu Kohama, David Graf, John Singleton, Joe Thompson and Frank Steglich. [1] Lin Jiao et al., arXiv:1308.0294.

29

Heusler Compounds, Spin Orbit coupling, Topological

Insulators and New Effects

Claudia Felser

MPI for Chemical Physics of Solids, Germany

Topological insulators are a hot topic in condensed matter physics. Many Heusler compounds with C1b structure are ternary semiconductors that are structurally and electronically related to the binary semiconductors. The diversity of Heusler materials opens wide possibilities for tuning the bandgap and setting the desired band inversion by choosing compounds with appropriate hybridization strength (by the lattice parameter) and magnitude of spin-orbit coupling(SOC, by the atomic charge). Based on first-principle calculations we demonstrate that around 50 Heusler compounds show band inversion similar to that of HgTe [1]. Many of these ternary zero-gap semiconductors (LnAuPb, LnPdBi, LnPtSb and LnPtBi) contain the rare-earth element Ln, which can realize additional properties ranging from superconductivity (for example LaPtBi) to magnetism (for example GdPtBi) and heavy fermion behaviour (for example YbPtBi).These properties can open new research directions in realizing the quantized anomalous Hall effect and topological superconductors. In AmN and PuTe a band gap is opened by correlation effects. In a family of semiconductors with the simple NaCl structure band gaps up to 0.4 eV were found [2]. This is not so surprising since the SOC should be large in Actinides. Heusler compounds are similar to a stuffed diamond, correspondingly, it should be possible to find the “high Z”' equivalent of graphene in a graphite-like structure or in other related structure types with 18 valence electrons and with inverted bands [3]. Indeed the ternary compounds, such as LiAuSe and KHgSb with a honeycomb structure of their Au-Se and Hg-Sb layers feature band inversion very similar to HgTe which is a strong precondition for existence of the topological surface states [4,5]. LiAuSe is a strong TI, whereas KHgSb a weak TI. Up to now there are no oxides which were identified to be topological insulators. BaBiO3 is an oxide which shows a band inversion similar to HgTe. We will discuss the necessary and sufficient conditions for new TI materials, based in symmetry and bonding arguments [3].

1. S. Chadov, X. Qi, J. Kübler, G. H. Fecher, C. Felser, S.-C. Zhang, Nature Mater. 2010, 9, 541 “Tunable multifunctional topological insulators in ternary Heusler compounds”

2. X. Zhang, HJ. Zhang, J. Wang, C. Felser, S.-C. Zhang, Science2012, 335, 1464 “Actinide Topological Insulator Materials with Strong Interaction”

3. L.Müchler, HJ. Zhang, S. Chadov, B. Yan, F. Casper, J. Kübler, SC. Zhang, C. Felser, Angew. Chem. Int. Ed.2012, 51, 7221“Topological Insulators from a Chemist’s Perspective”

30

4. B. Yan, L. Müchler, C. Felser, Phys. Rev. Lett. 2012, 109, 116406 “Prediction of weak topological insulators in layered semiconductors”

5.H.-J. Zhang, S. Chadov, L. Müchler, B. Yan, XL. Qi, J. Kübler, SC. Zhang, C. Felser, Phys. Rev. Lett. 2011, 106, 156402 “Topological Insulators in Ternary Compounds with a Honeycomb lattice”

6. B. Yan, L. Müchler, X.-L. Qi, S.-C. Zhang, C. Felser, Phys. Rev. B2012, 85, 165125“Topological insulators in filled skutterudites”

31

Dominant Triplet Pairing and Possible Weak Topological

Superconductivity in BiS2-based Superconductors

Qiang-Hua Wang

Nanjing University, China

We show that the newly discovered BiS2-based superconductors may have a dominant triplet pairing component, in addition to a subdominant singlet component arising from the spin-orbital coupling. The pairing respects time-reversal symmetry. The dominant triplet gap causes gap sign changes between the spin-split Fermi pockets. Within a pocket, the gap function respects $d^*_{x^2-y^2}$-wave symmetry, where the star indicates joint spin-lattice rotations. Below the Lifshitz filling level the gap is nodelss and the superconducting state is weak topological. Above the Lifshitz points the gap becomes nodal. The superconducting pairing and the time-reversal symmetry result from the strong spin-orbital coupling and the ferromagnetic-like spin fluctuations. The $d^*_{x^2-y^2}$-wave gap structure follows from the coexisting antiferromagnetic spin fluctuations.

32

Topological Phases in Mix Valence Compounds

Xi Dai


In this talk, I will propose that the mix valence phenomena in some of the rare earth compounds will naturally lead to non-trivial topology in band structure. One of the typical example is SmB6, where the intermediate valence of Sm generates band inversion at the X point and the non-trivial Z2 index. Other than SmB6, YbB6 and YbB12 are both mix valence compounds. By applying LDA+Gutzwiller to these materials, we find that YbB6 has non-trivial Z2 index, indicating that YbB6 is another three dimensional topological insulator with strong correlation effects. Our calculation also finds that YbB12 is a trivial insulator in the sense of Z2 but it can be classified as topological crystalline insulator with non-zero mirror Chern number. The electronic structure at finite temperature has also been studied using LDA+DMFT, indicating YbB6 is still in the mix valence region while YbB12 is quite close to the Kondo limit.

33

Spin-Orbital Physics in Frustrated Lattices

Alois Loidl

University of Augsburg, Germany.

Concepts of frustrated lattices and the importance of spin-orbit physics in correlated matter are exemplified on spinel compounds AB2X4, where magnetic ions can occupy either the tetrahedrally coordinated A-sites or the octahedrally coordinated B sites. The A-sites in the spinels form a diamond lattice, which is constituted by two interpenetrating fcc lattices. Depending on the ratio of the exchange-interaction strength, within one or in between two sublattices, frustration can dominate, spin order becomes suppressed in a broad range of parameters and the compounds exhibit unusual ground states, including spin liquids or spiral spin liquids.

The physics of A-site spinels is elaborated on compounds like MnSc2S4 and FeSc2S4

/1/, as well as on the alumino spinels, AAl2O4, with A = Mn, Fe and Co /2/. The iron spinels are only weakly Jahn-Teller active. FeSc2S4, where spin and orbital order become fully suppressed, constitutes one of the rare examples of a spin-orbital liquid and this system is close to a quantum critical point, where spin and orbital orders are suppressed as function of spin-orbit coupling /3/.

The B in the spinel lattice sites form a corner-sharing tetrahedral network, the famous pyrochlore lattice, which is strongly geometrically frustrated, with spin ice as one possible ground state. Chromium oxides, like ZnCr2O4 are representative examples, with exotic spin structures and new elementary excitations at low temperatures. In the chromium sulfides and selenides the lattice becomes slightly expanded, weakening the direct antiferromagnetic exchange and increasing the ferromagnetic Cr-X-Cr exchange, yielding strong bond frustration. These systems reveal a number of unusual ground state, like spin-driven Jahn-Teller effects or spin-driven ferroelectricity /4/.

The complexity of spin-orbital physics in frustrated lattices can become even enhanced, when both lattice sites are occupied by magnetic ions. FeCr2S4 will be discussed as a representative example. Originally interpreted as simple ferrimagnet with the onset of orbital order close to 10 K, we identified the appearance of a helical magnetic phase at low temperatures, driven by orbital fluctuation /5/ and we established a complex (H,T) phase diagram /6/. The possible onset of polar order at low temperatures and the appearance of unusual orbital excitations will be discussed in detail.

/1/ V. Fritsch et al., Phys. Rev. Lett. 92, 116401, 2005

/2/ N. Tristan et al., Phys. Rev. B 77, 094412, 2008

/3/ G. Chen et al., Phys. Rev. Lett. 102, 096406, 2009

/4/ T. Rudolf et al., New J. Phys. 9, 76, 2007; Phys. Rev. B 76, 174307, 2007

/5/ G. M. Kalvius et al., J. Phys. Condens. Matter 22, 052205, 2010

/6/ J. Bertinshaw et al., arXiv:1309.2140

34

Correlation Effects in Frustrated Systems: Triangular and

Honeycomb Lattices

Roser Valenti

Goethe-University, Frankfurt am Main, Germany

Correlated electronic systems with an additional complexity of a geometrically frustrated lattice provide an exciting ground for the study of several competing interactions among spin, orbital and lattice degrees of freedom.

In this talk we shall discuss the role of correlations in prototypical Mott systems like the triangular \kappa-(BEDT-TTF)_2X family of organic charge transfer (CT) salts, and the kagome system ZnCu3(OH)6Cl2 by considering a combination of density functional theory and manybody methods and will compare our results with experimental observations.

If time permits, I will make a detour to the hexagonal-based 5d system Na2IrO3.

35

Possible Spin Liquid State on a Honeycomb Lattice

Shi-Yan Li

Fudan University, China

The exotic spin liquid state is usually expected in the frustrated triangular or kagome lattices. However, for honeycomb lattice with both nearest antiferromagnetic exchange interaction J1 and next nearest antiferromagnetic exchange interaction J2, it also manifests frustration and may enter into a spin liquid state beyond certain J2/J1 value. In this talk, I will present our magnetic and thermodynamic measurements on a compound with honeycomb lattice, and show that it may be the first experimental realization of spin liquid state on a honeycomb lattice.

36

On the Dual Fermion Approach to Charge Order,

Spin Frustration, and Transport

Stefan Kirchner

MPI for the Physics of Complex Systems, Germany

Self-consistent dynamical approximations for strongly correlated fermion systems are particularly successful in capturing the dynamical competition of local correlations. In these, the effect of spatially extended degrees of freedom is usually only taken into account in a mean field fashion or as a secondary effect. As a result, critical exponents associated with phase transitions of the model have mean field character. Here, we demonstrate that a particular diagrammatic multi-scale method, the dual fermion method, anchored around local approximations are indeed capable of capturing the non mean-field nature of the critical point of the lattice model and to correctly describe the transition to mean field like behavior as the number of spatial dimensions increases [1]. In spin models with frustrated interactions, relevant to a wide range of materials, e.g. the $\kappa$-(BEDT-TTF)$_{2}$X family, the layered cobaltates, the delafossites, this approach is able to capture the dynamic interplay between electronic correlation and geometric frustration [2]. The dual fermion method can be extend to tackle systems far from equilibrium and has recently been used to interpret nonlinear transport data in strongly correlated nanostructures [3]. In collaboration with A. Antipov, E. Gull, W. Hanke, G. Li, E. Munoz, R. Rubtsov [1] A. Antipov, E. Gull, & S. Kirchner, in preparation. [2] G. Li, A. Antipov, A. Rubtsov, S. Kirchner, & W. Hanke, arXiv:1211.5093. [3] E. Munoz, C. Bolech, & S. Kirchner, PRL, 110, 016601 (2013).

37

Routes to Quantum Criticality in Heavy-fermion Systems

Hilbert v. Löhneysen

Kalsruhe Institute of Technology, Germany

Heavy-fermion systems are an ideal playground for studying the quantum phase transition (QPT) between paramagnetic and magnetically ordered ground states that in these systems is governed by the interplay of Kondo and RKKY interactions [1]. Two different routes have been identified by various experiments, i. e., the more traditional spin-density-wave [2] and the Kondo-breakdown [3] approaches. However, up to know an a-priori assignment of a given system to these different routes has not been possible. Furthermore, the role of the tuning parameter is an open issue. Dimensionality has been invoked as a possible criterion increasing fluctuations, but this has not been universally accepted [4]. Another source of fluctuations not included in the above approaches might be geometric frustration of magnetic moments, a route to quantum criticality well known for insulating magnets with competing interactions [5]. First experiments on metallic systems have recently been conducted. We will discuss recent experiments on the canonical partially frustrated system CePdAl where a QPT can be reached by substitution of Pd by Ni [6] and on the established QPT system CeCu6-xAux [7] to shed light on these issues. [1] H. v. Löhneysen et al., Rev. Mod. Phys. 79, 1015 (2007) [2] J. A. Hertz, Phys. Rev. B 14, 1165 (1976); J. A. Millis, Phys. Rev. B 48, 7113 (1993); T. Moriya and T. Takamoto, J. Phys. Soc. Japan 64, 960 (1995) [3] Q. Si et al., Nature 413, 804 (2001) [4] J. Custers et al., Nature Materials 11, 189 (2012) [5] B. Keimer and S. Sachdev, Physics Today 64 (2), 29 (2011) [6] V. Fritsch et al., arXive: 1301.6062 [7] A. Hamann et al., Phys. Rev. Lett. 110, 096404 (2013)

38

Exploring Quantum Criticality by Applying Chemical Pressure

Cornelius Krellner


Quantum critical phenomena fascinate solid-state physicists for quite some time now, as emerging phases of matter can be observed in the vicinity of quantum critical points (QCPs). Pressure, magnetic field, or chemical substitution are the common parameters to drive a material from one ground state to another and to explore the phase diagram. Whereas pressure is the most elegant way to tune the material, certain experiments are often very hard under external pressure and there is no way to apply negative pressure. Chemical substitution or chemical pressure is then often the only way to explore quantum criticality in more detail. For moderate, isoelectronical, and isostructural substitution the dominant effect on the ground state is usually the volume effect of the substituted atom, which can be both, positive or negative.

In this talk, I will present three recent cases, where chemical pressure was used to investigate ferromagnetic (FM) quantum criticality in heavy fermion systems. (1) The recent observation of a FM QCP in As-substituted YbNi4P2 (2) The emergence of FM order in Co-substituted YbRh2Si2 (3) Avoided FM QCP in Ru/As-substituted CeFePO.

(1) Steppke et al., Science 339, 933 (2013). (2) Lausberg et al., Phys. Rev. Lett. 109, 216402 (2013). (3) Jesche et al., to be published.

39

Electronic Correlations and Quantum Criticality in Iron Pnictides

Qimiao Si

Rice University, USA

In the iron pnictides, the normal state is a bad metal. As such, electron correlations are expected to play an important role. This has been further highlighted by the more recent developments in the iron chalcogenides. In this talk, I will address several aspects of the correlation effects, both in the normal and superconducting states. I will discuss the earlier theoretical studies that led to the proposal for a quantum critical point in the iso-electronically tuned iron pnictides [1]. Subsequent experiments have not only verified this in the isovalentP-doped iron arsenides [2], but also implicated a similar quantum critical point in the Ni- (electron-) doped materials [3]. I will also discuss the recent theoretical studies on the multi-orbital aspects of the electron correlations, which have led to an orbital selective Mott phase [4]; ARPES measurements have provided evidence for such a phase in the alkaline iron selenides[5]. The implications of such orbital selectivity on the superconducting properties, particularly the anisotropy of the superconducting gap and spin resonance excitation, will also be discussed [6,7]. [1] J. Dai, Q. Si, J.-X. Zhu, and E. Abrahams, PNAS 106, 4118 - 4121 (2009). [2] C. de la Cruz et al, PRL 104, 017204 (2010); Y. Luo et al., PRB 81, 134422 (2010); S. Kasahara et al, PRB 81, 184519 (2010); K. Hashimoto et al, Science 336, 1554 (2012); [3] X. Lu et al., PRL 110, 257001 (2013) [4] R. Yu and Q. Si, Phys. Rev. Lett. 110, 146402 (2013) and references therein. [5] M. Yi et al., Phys. Rev. Lett. 110, 067003 (2013). [6] R. Yu, J.-X. Zhu, and Q. Si, arxiv:1306.4184. [7] C. Zhang, R. Yu et al., submitted (2013).

40

Quantum Critical Point Hidden beneath the Superconducting

Dome in Iron-pnictides

Yuji Matsuda

Kyoto University, Japan

Whether a quantum critical point (QCP) lies beneath the superconducting dome has been a long-standing issue that remains unresolved in many classes of unconventional superconductors, notably cuprates, heavy fermion compounds and most recently iron-pnictides. The existence of a QCP may offer a route to understand: the origin of their anomalous non-Fermi liquid properties, the microscopic coexistence between unconventional superconductivity and magnetic or some exotic order, and ultimately the mechanism of superconductivity itself. The isovalent substituted iron-pnictide BaFe2(As1−xPx)2 offers a new platform for the study of quantum criticality, providing a unique opportunity to study the evolution of the electronic properties in a wide range of the phase diagram [1]. Recent experiments in BaFe2(As1−xPx)2 have provided the first clear and unambiguous evidence of a second order quantum phase transition lying beneath the superconducting dome[2][3][4]. Based on these results, a new phase diagram of iron-pnictide is discussed [5]. In collaboration with K. Hashimoto,S.Kasahara,Y. Mizumami, H. Shishido, T. Shibauchi(Kyoto),B. J. Arnold, A.Serafin, I.Guillamón, P. M. C. Rourke, P. Walmsley, C.Putzke, A. Carrington (Bristol), M.Tanatar, R.Prozorov (Ames), N. Salovich,R. W. Giannetta(Illinois) and A. H. Nevidomskyy (Rice). [1]S. Kasaharaet al. Phys. Rev. B 81, 184519 (2010). [2] K. Hashimoto et al. Science336, 1554 (2012) [3]P. Walmsleyet al. Phys. Rev. Lett.110, 257002 (2013). [4]K. Hashimoto et al. Proc. Natl. Acad. Sci. USA,110, 3293 (2013). [5] S. Kasahara et al. Nature, 486, 382 (2012).

41

Aspects of Fermiology in Correlated Metals

Jochen Wosnitza

Hochfeld-Magnetlabor Dresden (HLD), Germany

One of the most powerful methods to determine band-structure parameters in metals are measurements of magnetic quantum oscillations. By applying high magnetic fields, this can be done e.g. by detecting the oscillations in the field-dependent magnetization, called de Haas-van Alphen (dHvA) effect, or by resolving Shubnikov-de Haas (SdH) oscillations in the field-dependent resistivity. In combination with sophisticated band-structure calculations often a deeper understanding of the electronic properties of metals is gained. One example for such a joint effort of experimental and theoretical work is the finding and explanation of the field-induced band-structure change in CeBiPt. In this material, a drastic change of the electronic band structure, as seen in the SdH and Hall signals, is found above about 25 T. This field-induced Lifshitz transition can be understood by the splitting of the Ce-5d bands close to the Fermi energy due to the exchange interaction with the polarized Ce-4f states. Another example is the detection of Shubnikov-de Haas oscillations in electron-doped high-temperature superconductors that allowed to unravel the doping-dependent evolution of the Fermi-surface topology. The observed reconstruction of the Fermi surface gives evidence for the existence of a superlattice potential, the origin of which is still under debate. Finally, the comprehensive investigation of the Fermi-surface evolution with Yb substitution in Ce1−xYbxCoIn5 showed a continuous transition from the heavy-fermion limit (CeCoIn5) to the mixed-valence limit in YbCoIn5, where an Yb valence of +2.3 is proven. For a small Yb concentration, x = 0.1, the band-structure topology and the effective masses remain nearly unchanged compared to CeCoIn5. This contrasts clearly modified Fermi surfaces and light, almost unrenormalized effective masses for x = 0.2 and above. These observations contrast the heavy-fermion physics observed in specific-heat and resistivity data even for high Yb concentrations.

42

Impurity in the Quantum Critical Superconductor CeCoIn5

Tuson Park

SungKyunKwan University, Korea

Superconductivity in strongly correlated compounds is often very sensitive to a disorder. Proximity to magnetically ordered states in these superconductors implies that magnetism plays an important role in the formation of superconductivity. In most cases, however, intrinsic disorder associated with electron/hole doping to parent compounds leads to a glassy behavior, puzzling the relationship between superconductivity and magnetism. The heavy fermion superconductor CeCoIn5 is one of the few examples that are quantum critical without chemical substitution, therefore offering the opportunity to explore the consequences of a chemical disorder.In this talk, we discuss Cd-doping effects on the quantum critical superconductors CeCoIn5, where a slight amount of Cd impurities induce magnetism. Applied pressure was expected to reverse the doping effects, which turned out to be otherwise. Experimental evidences underlie that extended magnetic objects are formed surrounding Cd impurities and the overlapping among the objects is the source of the long-range ordered antiferromagnetic state.

43

Exploring the Heavy-fermion Superconductor

CeIrIn5 under Pressure

Xin Lu


The heavy-Fermion superconductor CeIrIn5 has two superconducting (SC) domes in the combined phase diagram of Rh doping and physical pressure. It has been proposed that SC in the pressuredome is due to valence fluctuation, rather than the general spin-fluctuations believed in CeRhIn5 or CeCoIn5. We applied the field-rotating heat capacity measurements with the ac calorimetryunder pressure and vector magnet technique to probe thegap nodal positions of the superconductivity and the observed four-fold oscillations in the heat capacity under different pressures confirm the d_{x^2-y^2} order parameter symmetry even deep inside the pressure SC dome[1], consistent with the spin-fluctuation scenario. The SC resistive transition shows an anisotropy between [100] and [001], indicating a textured structure of superconductivity in CeIrIn5 before the bulk SC at 0.4 K.This textured superconductivity is widely observed in the heavy-fermion systems such as CeRhIn5 due to a coexisting order[2]. For the 1.0% Cd-doped CeIrIn5, the long-range AFM is suppressed under hydrostatic pressure around 3 GPa and superconductivity reemerges with Tc ~ 1 K, indicating a quitereversible tuning of doping and pressure as in the case of CeCoIn5. However, the relationship between AFM and SC in the CeIrIn5 system deserves further careful studies. This work is in collaboration with Hanoh Lee, Tuson Park, Joe Thompson, F. Ronning, E. Bauer and Z. Fisk. Reference: [1] Xin Lu et al., Physical Review Letters, 2012,108,027001 (2012) [2] Tuson Park et al., Physical Review Letters, 2012, 108, 077003(2012)

44

Revealing Multiple Density Wave Orders in Non-superconducting

Titanium Oxypnictide Na2Ti2As2O

Nan-Lin Wang


We present an optical spectroscopy study on the single crystal of Na2Ti2As2O, a sister compound of superconductor BaTi2Sb2O. The study reveals unexpectedly two density wave phase transitions. The first transition at 320 K results in the formation of a large energy gap and removes most part of the Fermi surfaces. But the compound remains metallic with residual itinerant carriers. Below 42 K, another density wave phase transition with smaller energy gap scale occurs and drives the compound into semiconducting ground state. These experiments thus enable us to shed light on the complex electronic structure in the titanium oxypnictides. Work done with Y. Huang, H. P. Wang, R. Y. Chen, X. Zhang, P. Zheng, Y. G. Shi.

45

Correlated States near Magnetic and Structural

Quantum Phase Transitions

Malte Grosche

University of Cambridge, UK

Signatures of Fermi liquid breakdown are widely observed in narrow band metals on the threshold of magnetism, and in transition metal systems the underlying mechanisms can be investigated without the Kondo physics associated with f-electron compounds. In the transition metal compound NbFe2, as in ZrZn2 and MnSi above the critical pressure, a T3/2 power law temperature dependence of the resistivity is observed over a wide region of the phase diagram, which remains a challenge to theory [1]. In constrast to ZrZn2 and MnSi, however, the transition into ferromagnetic order on cooling is preceded by a magnetic state of unidentified nature. NbFe2 can be tuned effectively by pressure, transverse field and chemical substitution, and high quality single crystals are now available. This motivates a detailed investigation of the unidentified magnetic state by bulk and spectroscopic techniques and enables a closer look at the possibility of transverse-field tuned quantum criticality.

Further to purely magnetic quantum phase transitions, structural transitions become increasingly likely with growing material complexity. The cubic superconductor Sr3Ir4Sn13 undergoes a second order superlattice transition on cooling through T* = 147 K. High pressure or chemical substitution with Ca suppress T* continuously and lead to a structural quantum phase transition [2]. We observe a linear temperature dependence of the resistivity near the quantum phase transition, which extends down to the enhanced superconducting transition temperature Tc, suggesting that parts of the phonon spectrum soften over a wide region of reciprocal space.

[1] M. Brando et al., PRL 101, 026401(2008) [2] L. E. Klintberg et al., PRL109, 237008 (2012)

46

Effects of Pressure on Certain Correlated Electron System

Chang-Qing Jin


High Pressure plays significant role in shaping quantum states of correlated electron system. Pressure modifies spin, charge or orbital properties that in turn change physical properties of correlated electron system. We will introduce our recent works[1~8] of effects of pressure on iron based superconductors, high Tc cuprates, topological insulators etc in this presentation. The works presented are supported by NSF & MOST of China through research projects. We thank our collaborators for their significant contributions. References: 1. C. Q. Jin et al; Proc. Natl. Acad. Sci. USA, 105, 7115 (2008) 2. X. C. Wang et al, Solid State Communications 148, 538 (2008) 3. J.G. Zhao et al, J. Am. Chem. Soc.130, 13828 (2008) 4. Q. Q. Liu et al., J. Am. Chem. Soc. 133, 7892 (2011) 5. J. S. Zhou et al. Phys. Rev. Lett., 101, 77206(2008). 6. J. G. Cheng et al., Phys. Rev. Letts. 108, 236403 (2012) 7. J. L. Zhang et al., Proc. Natl Acad. Sci. 108, 24 (2011) 8. J. Zhu et al., Scientific Reports | 3 : 2016(2013)

47

Weak Ferromagnetism with the Kondo Screening

Effect in the Kondo Lattice Systems

Guang-Ming Zhang

Tsinghua University, China

We carefully consider the interplay between ferromagnetism and the Kondo screening effect in the conventional Kondo lattice systems at both zero temperature and finite temperatures. Within an effective mean-field theory for small conduction electron densities, a complete phase diagram has been determined. In the ferromagnetic ordered phase, there is a characteristic temperature scale to indicate the presence of the Kondo screening effect. We further find two distinct ferromagnetic long-range ordered phases coexisting with the Kondo screening effect: spin fully polarized and partially polarized states. A continuous phase transition exists to separate the partially polarized ferromagnetic ordered phase from the paramagnetic heavy Fermi liquid phase. These results may be used to explain the weak ferromagnetism observed recently in the Kondo lattice materials.

References:

1. Guang‐Bin Li, Guang‐Ming Zhang, and Lu Yu, Physical Review B 81, 094420 (2010).

2. Yu Liu, Guang‐Ming Zhang, and Lu Yu, Physical Review B 87, 134409 (2013).

48

From Dirac Fermion to Dirac Heavy Fermion: Emergent

Semi-metallic Heavy Fermion Phase on a Honeycomb Lattice

Jian-Hui Dai

Hangzhou Normal University, China

Coupling of Dirac fermions of a conduction band to a local moment lattice does not immediately lead to a heavy fermion state due to the pseudo-gap nature of the itinerant electron host. Based on a slave boson analysis and general considerations, we show that the heavy fermion excitations with a Diraclike semi-metal dispersion can emerge out of a two-dimensional Anderson lattice model with honeycomb structure by tuning electron fillings away from the half-filling. We also discuss the relevance of this semi-metallic heavy fermion phase in the contexts of topological Kondo insulator and magnetic quantum phase transitions. This work was done in collaboration with X.Y. Feng, Chung‐Hou Chung, and Qimiao Si.

49

Heavy Electron Kondo Liquid and Long-range Orders

Yi-Feng Yang


Anomalous normal state behaviors in heavy fermion materials have posed severe challenge to our current understanding of heavy fermion physics. In previous work, we have shown that these anomalies can all be attributed to an unusual emergent heavy electron state, the Kondo liquid, that displays universal behavior below the coherent temperature T* [1,2]. Here I will report some recent progresses and show that the Kondo liquid picture also provides a simple way to understand the low temperature orders [3,4,5]. Our work suggests a close resemblance between heavy fermion physics and cuprate physics. 1. Yi-feng Yang and David Pines, Phys. Rev. Lett. 100, 096404 (2008). 2. Yi-feng Yang et al., Nature 454, 611 (2008). 3. N. apRoberts-Warren et al., Phys. Rev. B 83, 060408(R) (2011) 4. Yi-feng Yang and David Pines, Proc. Natl. Acad. Sci. USA 109, E3060 (2012). 5. K. R. Shirer et al., Proc. Natl. Acad. Sci. USA 109, E3067 (2012).

50

Field-induced Berezinskii-Kosterlitz-Thouless Scenario in a

2-Dimensional Spin-dimer System

Michael Lang


Weakly-coupled spin-1/2 dimer systems exposed to a sufficiently strong magnetic field offer exciting possibilities for studying critical phenomena under well-controlled conditions [1]. Prominent examples include the Bose-Einstein condensation (BEC) of magnetic triplet excitations in three dimensionally (3D)-coupled materials [1] and Luttinger-liquid behaviour in quasi-1D systems [2]. It is thus natural to ask whether dimers, properly combined, can also be used to explore phenomena restricted to 2D. For interacting particles in 2D, long-range magnetic order and BEC are destroyed by thermal fluctuations as was rigorously shown by Mermin and Wagner. Instead, according to Berezinskii, Kosterlitz and Thouless (BKT), a topological order may occur resulting from the binding of vortex-antivortex pairs. Here we report on a chemically-constructed multilayer bulk magnet, C36H48Cu2F6N8O12S2 (TK91), composed of molecule-based pairs of spin S = 1/2 dimers, where, by the application of a magnetic field, a gas of magnetic excitations is formed. Based on low-temperature measurements of the magnetic susceptibility and specific heat, combined with Density Functional Theory and Quantum Monte Carlo calculations, we conclude that these excitations have a distinct 2D character, implying the emergence of vortices and antivortices, and that the field-induced state revealed at low temperatures is likely a manifestation of the BKT scenario. This work is in collaboration with M. Lang, U. Tutsch1, B. Wolf1, Y. Tsui1, S. Wessel2, H. Jeschke3, I. Ophale4, T. Saha-Dasgupta5, R. Valentí3, A. Brühl1, K. Remović-Langer1, T. Kretz6, H.-W. Lerner6, M. Wagner6 [1] T. Giamarchi et al., Nature Physics 4, 198 (2008). [2] Ch. Rüegg et al., Phys. Rev. Lett. 101, 247202 (2008).

51

Low-frequency Charge Carrier Dynamics at the Mott Transition in

the Quasi-2D Organic Conductors κ-(BEDT-TTF)2X

Jens Müller

Johann Wolfgang Goethe-University Frankfurt, Germany

The quasi-two-dimensional organic charge-transfer salts κ-(ET)2X are considered model systems for studying electron-electron correlations in reduced dimensions.

Depending on the anion X, either a Mott-insulating and antiferromagnetically-ordered or a metallic and superconducting ground state is realized. Likewise, subtle chemical modifications of the ET donor molecules as well as moderate hydrostatic pressure modulate the ratio of bandwidth W to on-site Coulomb repulsion U, resulting in a universal phase diagram of a bandwidth-controlled Mott transition. Both the nature of the static and dynamic criticality of the Mott transition and the influence of disorder on the metal insulator transition (MIT) currently are in the focus of intense experimental and theoretical efforts. In addition, we recently have reported on the surprising observation of multiferroicity within the Mott insulating state that is suggestive of electric-dipole driven magnetism [1].

In this talk, we report on a systematic study of the low-frequency dynamics of the charge carriers of various κ-(ET)2X salts, with particular focus on Mott transition, by utilizing fluctuation (noise) spectroscopy as a powerful new tool to study these materials. For the first time, we have observed a pronounced and sudden slowing down of the carrier dynamics near the finite-temperature critical endpoint of the Mott transition [2]. In these experiments, the low-frequency noise power spectral density of the resistance/conductance fluctuations of fully deuterated κ-(D8-ET)2Cu[N(CN)2]Br exhibits a strong increase near the critical point, accompanied by a substantial shift of spectral weight to low frequencies.

We also present new results on partially deuterated κ-[(H8-ET)0.2(D8-ET)0.8]2Cu[N(CN)2]Br, which is located very close to the critical region of the generalized phase diagram, and where the bandwidth can be reversibly tuned by varying the cooling rate of the sample. The lowfrequency resistance fluctuations show an increasingly divergent behavior when tuning the sample closer to the critical point. We compare our results to other MITs of different origin and dimensionality and speculate that diverging low-frequency fluctuations and correlated electron dynamics may be universal features of any MIT.

This work is in collaboration with B. Hartmann, R. Rommel, D. Zielke, J. Polzin. [1] P. Lunkenheimer, J. Müller et al., Nature Materials 11, 755 (2012). [2] J. Brandenburg, J. Müller, J.A. Schlueter, New J. Phys. 14, 023033 (2012).

52

Quantum Spin Liquids at the Vicinity of Mott Transition

Yi Zhou


We study quantum spin liquid states (QSLs) at the vicinity of metal-insulator transition. Assuming that the low energy excitations in the QSLs are labeled by “spinon” occupation numbers with the same Fermi surface structure as in the corresponding metal (Fermi-liquid) side, we propose a phenomenological Landau-like low energy theory for the QSLs and show that the usual U(1) QSLs with spinon Fermi surface is a representative member of this class of spin liquids. Based on our effective low energy theory, an alternative picture to the Brinkman-Rice picture of Mott metal-insulator transition is proposed. The charge, spin and thermal responses of QSLs are discussed under such a phenomenology.

53

Non-Fermi Liquid and Exotic Heavy-fermion Behavior in the Filled

Skutterudites XPt4Ge12 (X=Ce, Sm)

Michael Nicklas

Max Planck Institute for Chemical Physics of Solids, Dresden Germany

Recently, a new family of filled skutterudites based on a framework of platinum and germanium with the chemical formula XPt4Ge12 has been discovered [1,2]. They exhibit a large variety of equally intriguing physical properties. Here, we will discuss the two examples SmPt4Ge12 and CePt4Ge12. SmPt4Ge12 exhibits an exotic heavy-fermion ground state which is remarkably insensitive against high magnetic fields [3]. The usual magnetic Kondo effect seems to be too weak to produce the large Sommerfeld coefficient. We suggest an alternative mechanism based on the ‘rattling’ Sm cation exhibiting a low-lying Einstein mode with respect to the Sm crystal-field doublet–quartet excitation which is responsible for the large hybridization leading to the exotic heavy-fermion state [3,4]. CePt4Ge12 represents a system at the border between intermediate valence and Kondo lattice behavior [5]. Substitution of Ge by Sb drives the system into a strongly correlated and, ultimately, upon further increasing the Sb concentration, an antiferromagnetically ordered state. We will discuss the delicate interplay of emerging Kondo physics and the formation of a local 4f moment. The observed extended non-Fermi-liquid region can be understood in the framework of a Kondo-disorder model [6]. In collaboration with R. Gumeniuk, W. Schnelle, S. Kirchner, R. Borth, M. Schöneich, H. Rosner, K. O. Kvashnina, Y. Skourski, A. A. Tsirlin, A. Ormeci, U. Burkhardt, M Schmidt, U Schwarz, M Ruck, H. Borrmann, A. Leithe-Jasper, F. Steglich, and Yu. Grin 1) E. Bauer et al., Phys. Rev. Lett. 99, 217001 (2007). 2) R. Gumeniuk et al., Phys. Rev. Lett. 100, 017002 (2008). 3) R. Gumeniuk et al., N. J. Phys. 12, 103035 (2010). 4) T. Hotta, J. Phys. Soc. Japan 77, 103711 (2008). 5) R. Gumeniuk et al., J. Phys.: Condens. Matter 23, 465601 (2011). 6) M. Nicklas et al., Phys. Rev. Lett. 109, 236405 (2012).

54

Local Kondo Scattering Detected by Nernst Effect

Pei-Jie Sun


We analyze the large, strongly temperature-dependent Nernst coefficient observed for CeCu2Si2 and its La-doped variants between T = 2 K and room temperature, and show evidence that the enhanced Nernst coefficient in heavy-fermion material is determined by the asymmetry of the on-site Kondo (conduction electron-4f electron) scattering rate. Based on this analysis and taking into account the measured Hall mobility H, we found the highly unusual thermopower S of these systems can be quantitatively described by a relation S(T) = - (T)/H(T) for the first time. This explicitly demonstrates that the thermopower of heavy-fermion compounds originates from the local, asymmetric Kondo scattering process over a wide temperature range from far above to well below the coherence temperature (20 K for CeCu2Si2). Our results suggest that the Nernst effect can act as a proper probe of local charge-carrier scattering. This also promises an impact on exploring the unconventional enhancement of the thermopower in correlated materials suited for potential applications. [1] Peijie Sun and Frank Steglich, Phys. Rev. Lett. 110, 216408 (2013).

55

Competing Magnetic Phases in Yb(Rh1-xCox)2Si2

Oliver Stockert

Max Planck Institute for Chemical Physics of Solids, Dresden, Germany

In contrast to systems at a spin-density-wave instability like CeCu2Si2, the heavy-fermion compound YbRh2Si2 exhibits unconventional quantum critical behavior in thermodynamic and transport properties. The magnetic order and the critical spin dynamics are at the origin of this unusual behavior. Due to the low ordering temperature and the small ordered moment in YbRh2Si2 neutron scattering experiment have failed so far in detecting the magnetic structure. We followed the route of substituting Co for Rh in YbRh2Si2 up to pure YbCo2Si2. This results in a stabilization of the magnetic order and an increase of the ordering temperature. Extensive neutron scattering has been performed to shed light on the magnetism in Yb(Rh1-xCox)2Si2. The spin-wave dispersions in the low-temperature commensurate and the high-temperature incommensurate antiferromagnetic phase of YbCo2Si2 have been determined. They reveal a substantial softening of the magnons along [110] in the incommensurate phase suggesting possible ordering wave vectors for YbRh2Si2. Furthermore, our neutron scattering as well as the magnetization measurements on the alloying series Yb(Rh1-xCox)2Si2 indicate the importance of ferromagnetic correlations/order for a certain range of Co content in this heavy-fermion system. We will discuss our results in comparison to other quantum critical compounds. *Work performed in collaboration with A. Hannaske, S. Capelli, S. Matas, K. Schmalzl, W. Schmidt, D. Quintero Castro, K. Habicht, F. Steglich.

56

Vacancy Order and Magnetic Excitations in the 245 Fe-based

Superconductors

Wei Bao

Renmin University of China

The one-out-of-five Fe vacancy order in A2Fe4Se5 superconductors (A=K, Rb, Cs, Tl/K or Tl/Rb) [1-3] is found to exist in a wide composition range of KxFe2-ySe2 at low temperature, even in K2Fe3Se4 (234) [4]. The degree of the Fe vacancy order has been shown to be the determining factor for metallic transport in normal state and for the occurrence of superconductivity [4], similar to our previous result on the 11 iron selenide superconductors [5], for which bulk superconductivity is also destroyed by disorder-induced electron localization. At higher temperature, the one-out-of-five vacancy order coexists with the one-out-of-four Fe vacancy order, which is understandable in the 2-level statistical physics model [4,6]. A common mistake in current literature is to use the observation of the one-out-of-five vacancy pattern to identify the 245 sample composition.

The four spin clusters in the antiferromagnetic order of the one-out-of-five vacancy ordered lattice in KxFe2-ySe2 [1,3,4] is found also to be an inciprient antiferromagnetic order in the 11 superconductors [7]. Magnetic excitations from a 245 superconductor has been measured and they can be described by spin-wave theory with exchange interactions extending up to the second nearest neighbors, consistent with insights from the first-principle theory on the Fe-based materials [8].

[1] W. Bao et al., Chin. Phys. Lett. 28, 086104 (2011) [2] P. Zavalij etal., Phys. Rev. B 83, 132509 (2011) [3] F. Ye et al., Phys. Rev. Lett. 107, 137003 (2011) [4] W. Bao et al., Chin. Phys. Lett. 30, 027402 (2013) [5] T.J. Liu et al., Nat. Materials 9, 716 (2010) [6] W. Bao, Chin. Phys. B 22, 087405 (2013) [7] V. Thampy et al., Phys. Rev. Lett. 108 107002 (2012) [8] S. Chi et al., Phys. Rev. B 87 100501(R) (2013)

57

Insulator-Metal-Superconductor Transitions in Cuprate

Superconductors and Iron-Based Superconductors

Xing-Jiang Zhou


The parent compound of the copper-oxide high temperature superconductors is a Mott insulator. Superconductivity is realized by doping an appropriate amount of charge carriers. How a Mott insulator transforms into a superconductor is crucial in understanding the unusual physical properties of high temperature superconductors and the superconductivity mechanism. I will report high resolution angle-resolved photoemission (ARPES) measurement on heavily underdoped Bi2Sr2-xLaxCuO6+　 system[1]. The electronic structure of the lightly-doped samples exhibit a number of characteristics: existence of an energy gap along the nodal direction, d-wave-like anisotropic energy gap along the underlying Fermi surface, and coexistence of a coherence peak and a broad hump in the photoemission spectra. Our results reveal a clear insulator-superconductor transition at a critical doping level of ~0.10 where the nodal energy gap approaches zero, the three-dimensional antiferromagnetic order disappears, and superconductivity starts to emerge. These observations clearly signal a close connection between the nodal gap, antiferromagnetism and superconductivity.

In the single-layer FeSe/SrTiO3 film, upon varying the electron doping level, similar insulator-metal-superconductor transition is observed via high resolution ARPES measurements. The implications of the results will also be discussed.

[1]. Yingying Peng, Jianqiao Meng, Daixiang Mou, Junfeng He, Lin Zhao, Yue Wu, Guodong Liu, Xiaoli Dong, Shaolong He, Jun Zhang, Xiaoyang Wang, Qinjun Peng, Zhimin Wang, Shenjin Zhang, Feng Yang, Chuangtian Chen, Zuyan Xu, T. K. Lee and X. J. Zhou, arXiv:1302.3017, to appear in Nature Communications.

58

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59

Reentrant Superfluidity in Polarized Single Component Fermi Gases

with Dipolar Interactions

Yanming Che and Qijin Chen

Department of Physics, Zhejiang University, China

Quantum degenerate polar molecules and atoms have been made available experimentally [1][2], which provide a platform for exploring new phases of quantum gases where dipole-dipole interaction (DDI) plays a dominant role. In contrast to the widely studied isotropic and short range interactions in dilute atomic gases, the DDI is of long range and spatially anisotropic. The relative DDI strength can be tuned via external electrical field in the case of polar molecules or via tuning the Fermi energy (or density) in the case of magnetic atoms. Existing theorieson dipolar superfluidity are mostly based on mean field treatments, which are inadequate in treating the moderate and strong coupling regimes. Here we study theoretically the superfluidity of polarized single component 3D dipolar Fermi gases from weak to strong coupling regimes, within a pairing fluctuation theory[3][4]. Effects of finite temperature and pseudogap are addressed. One remarkable phenomenon is the re-entrant behavior of Tc in the T-g phase diagram, where g is the DDI strength. There exists a range of DDI where the system favors a pair density wave (or supersolid) state rather than Bose-Einstein condensation of pairs of zero momentum. This phenomenon is a result of the interplay of the long range nature and anisotropic properties of DDI. Transport properties including superfluid density and heat capacity below Tc are calculated as well, throughout the BCS-BEC crossover. When a 3D isotropic harmonic trap is included using a local density approximation (LDA), the density profile broadens with increasing temperature whereas it shrinks with increasing DDI strength, similar to its s-wave counterpart. References: [1] Mingwu Lu, Nathaniel Q. Burdick, and Benjamin L. Lev, Phys.Rev. Lett. 108, 215301 (2012). [2] K.-K. Ni, S. Ospelkaus, D. Wang, G. Quemener, B. Neyenhuis, M. H. G. de Miranda, J. L. Bohn, J. Ye, D. S. Jin, Nature 464, 1324-1328 (2010) [3] Q. J. Chen, J. Stajic, S. N. Tan, and K. Levin, Phys. Rep. 412, 1(2005). [4] Q. J. Chen, Ioan Kosztin, Boldizsar Janko, K. Levin, Phys. Rev. Lett. 81, 4708 (1998).

60

Asymptotical Description of the Ground State in the Strongly

Dissipative Quantum System

Shu He and Qing-Hu Chen


The standard Kondo model can be extended to various Bose-Fermi Kondo models including the coupling of the impurity to continuous bosonic baths described by a power-law density of states. Among them, spin-Boson model with Ohmic and sub-Ohmic baths is well known to undergo continuous quantum phase transitions. But the criticality is still highly controversial to date[1]. The genuine description of the ground state is still lacking at least in the analytical sense. Several advanced numerical approaches have been developed[2-5], but the bosonic state can not be described clearly. E.g. in the numerical renormalization group technique, the bosonic Hilbert-space truncation error is not easily avoided.

By using extended bosonic coherent states, a new technique to solve the spin-boson model in the delocalized phases systematically is proposed. Asymptotical description of the ground state in the strongly dissipative quantum system without variational parameters [6] is given, several physical quantities are analyzed, and consistent picture is hopefully arrived.

[1] S. Kirchner, K. Ingersent, and Q. Si, Phys. Rev. B 85, 075113 (2012) [2] R. Bulla, N.-H. Tong, and M. Vojta, Phys. Rev. Lett. 91, 170601 (2003). [3] A. Winter, H. Rieger, M. Vojta, and R. Bulla, Phys. Rev. Lett. 102, 030601 (2009). [4] A. Alvermann and H. Fehske, Phys. Rev. Lett. 102, 150601 (2009) [5] Y.-Y. Zhang, Q.-H. Chen, and K.-L. Wang, Phys. Rev. B 81, 121105(R) (2010). C. Wang and Q.-H. Chen, New Journal of Physics, 15 , XXX(2013) , in press [6] Q. -B. Ren and Q. -H. Chen, Chinese Physics letters 22, 2914(2005); S. Bera et al., arXiv: 1301.7430; 1307.5681

61

(La1-xBax)(Zn1-xMnx)AsO: A two-dimensional 1111-type Diluted

Magnetic Semiconductor in Bulk Form

Cui Ding[1], C. Q. Jin[2], Y. J. Uemura[3], F. L. Ning[1] [1] Department of Physics, Zhejiang University, Hangzhou 310027, China

[2] Beijing National Laboratory for Condensed Matter PhySsics and Institute for Physics,

Chinese Academy of Sciences, Beijing 100190, China [3]Department of Physics, Columbia University, New York , 10027, USA

We report the synthesis and characterization of a bulk diluted magnetic semiconductor (La1-xBax)(Zn1-xMnx)AsO with a layered crystal structure identical to that of the 1111-type FeAs superconductors. No ferromagnetic order occurs with (Zn,Mn) substitution in the parent compound LaZnAsO without charge doping. Together with carrier doping via (La,Ba) substitution, a small amount of Mn substituting for Zn results in ferromagnetic order with TC up to∼40 K, although the system remains semiconducting. Muon spin relaxation measurements confirm the development of ferromagnetic order in the entire volume, with the relationship between the internal field and TC consistent with the trend found in (Ga,Mn)As and the 111-type Li(Zn,Mn)As and the 122-type (Ba,K)(Zn,Mn) 2As2 systems.

62

Close Relationship between Superconductivity and the Bosonic Mode

in Ba0.6K0.4Fe2As2 and Na(Fe0.975Co0.025)As

ZhenyuWang1,2, Huan Yang1, Delong Fang1, Bing Shen2, Qiang-HuaWang1, Lei Shan2,

Chenglin Zhang3, Pengcheng Dai2,3 and Hai-HuWen1

1Center for Superconducting Physics and Materials, National Laboratory of Solid State

Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China, 2National Laboratory for Superconductivity, Institute of Physics and National Laboratory for

Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China, 3Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee

37996-1200,USA.

A central issue in the high-temperature superconductivity has been the microscopic origin of the superconducting pairing. Right now, it remains unclear in iron pnictides whether there is a bosonic mode from the tunnelling spectrum, which has a close and universal relationship with superconductivity as well as with the observed spin excitation . Here, on the basis of measurements of scanning tunnelling spectroscopy, we show clear evidence of a bosonic mode with energy identical to that of the neutron spin resonance in two completely different systems, Ba0.6K0.4Fe2As2 and Na(Fe0.975Co0.025)As, with different superconducting transition temperatures. In both samples, the superconducting coherence peaks and the mode feature vanish simultaneously inside the vortex core or above the transition temperature Tc, indicating a close relationship between superconductivity and the bosonic mode. Our data also demonstrate a universal ratio between the mode energy and superconducting transition temperature, that is Ω/kBTc ~4.3, which underlines the unconventional nature of superconductivity in the iron pnictide superconductors.

63

Magnetic Penetration Depth of Noncentrosymmetric

Superconductor BiPd

L. Jiao1, J. L. Zhang1, Y. Chen1, J. Chen1, B. H. Fu1,Y. M. Shao1,Y. Hu1,J. Y. Feng1,B. Joshi2,S. Ramakrishnan2,and H. Q. Yuan1*

1Department of Physics and Center for Correlated Matter,Zhejiang University, China 2Tata Institute of Fundamental Research, Colaba, Mumbai 400005, India

We report measurements of the magnetic penetration depth (λ(T)) on high-quality single crystalsof the noncentrosymmetric superconductor BiPd, with Tc≈3.7K.1 Multiple superconductinggaps have been observed for H∥b and H⊥b respectively.

But the temperature dependence of λ(T)is quite different for supercurrent along

different axis, which is also observed by point contact Andreev reflection spectra.2λ(T) shows exponential behavior for H//b below Tc/3, which is close to the predictionof s-wave gap function in BCS theory. For H⊥b, it followsT3law, indicating the contributionof multi-gap to the superconductivity in the ab and ac plane. These observations provide evidence of complex order parameter in thismaterial, which might attributed to the complicated band structure (conventional multiband scenario) orthe lift of spin degenerated band by a strongantisymmetric spin-orbit coupling. In the later case, the spin-triplet component will dominant. References [1] B. Joshi, A. Thamizhavel, and S. Ramakrishnan, Phys.Rev. B, 84, 064518 (2011). [2] M. Mondal, B. Joshi, S. Kumar, A. Kamlapure, S. C. Ganguli, A. Thamizhavel, S. S. Mandal, S. Ramakrishnan, andP. Raychaudhuri, Phys. Rev. B, 86, 094520 (2012).

64

Vortex Pinning from Conformal Pinning Arrays in Type-II

Superconductors: Time-dependent Ginzburg-Landau Dynamical Study

Huan Liu, Fei Qi, and Qing-Hu Chen

Department of Physics, Zhejiang University, Hangzhou 310027,China

Recently, conformal pinning arrays, topological perfect two-dimensional structures, easily introduced in the superconducting films, was demonstrated to produce much high critical currents over a wide range of magnetic fields by molecular dynamical simulations[1] and experimentally [2]. However, some features inherent to vortex motion have not been properly considered by molecular dynamics. Especially, one to one mapping the vortex to a particle breaks down at higher driven where the vortex displacement are highly anisotropic. More over the driven elongated vortices are eventually transformed into phase slip lines [3].

We will theoretically use the time-dependent Ginzburg-Landau (TDGL) simulations in terms of the time-dependent complex superconducting order parameter, which is very close to the real description of the vortices. In contrast with previous TDGL, we will introduce the fast Fourier transform to treat the boundary condition transverse to the driven direction to facilities the simulation and remove the surface barrier for the vortices. In this way, we can get more reasonable results for the pinning effects.

We will also use TDGL to study the ratchet effect induced by the artificial conformal pining arrays. Jumps in the IV curves in two opposite currents are clearly observed, and can be explained in terms of phase slip line and vortex stream picture. The jump can not be obtained by molecular dynamical simulations. This ratchet effect inside the sample is different from that from surface barrier [4].

[1] D. Ray et al., Phys. Rev. Lett. 110, 267001(2013); [2] Y. L. Wang et al., Phys. Rev. 87, 220501(R) (2013). [3] A. V. Silhanek et al., Phys. Rev. Lett. 104, 017001 (2010) [3] D. Cerbu et al., New Journal of Physics 15, 063022 (2013)

65

Unexpected Giant Superconducting

Fluctuation and Anomalous Semiconducting Normal State in

NdO1-xFxBi1-yS2 Single Crystals

Jianzhong Liu1†, Delong Fang1†, Zhenyu Wang2†, Jie Xing1, Zengyi Du1,

Xiyu Zhu1*, Huan Yang1*, Hai-Hu Wen1*

1Center for Superconducting Physics and Materials, National Laboratory of Solid State

Microstructures and Department of Physics, Nanjing University, Nanjing 210093, China 2 National Laboratory for Superconductivity, Institute of Physics and National Laboratory for

Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China

The BiS2-based superconductors were discovered recently. The superconductivity has been proved by many other groups. Since the previous experiments were all done on polycrystalline samples, therefore there remains a concern whether the superconductivity is really derived from the materials intrinsically or from some secondary phases. Experiments on single crystals are highly desired. In this paper, we report the successful growth of the NdO1-xFxBi1-yS2 single crystals. Resistive and magnetic measurements reveal that the bulk superconducting transition occurs at Tc = 4.83 K, while an unexpected giant superconducting fluctuation appears at temperatures as high as 2-4 kBTC. Analysis based on the anisotropic Ginzbaug-Landau

theory gives an anisotropy 45~30/ abc mm＝ . Two gap features with

magnitudes of about 3.50.3meV and 7.51 meV were observed by scanning tunneling spectroscopy. The smaller gap is associated with the bulk superconducting

transition yielding a huge ratio cBs Tk/2 1 =16.8, the larger gap remains up to about 26

K. The normal state recovered by applying a high magnetic field shows an anomalous semiconducting behavior. All these suggest that the superconductivity in this newly discovered superconductor cannot be formatted into the BCS picture.

66

The Synthesis and 31P NMR Study LiFeP

Huiyuan Man, and Fanlong Ning*

Department of Physics, Zhejiang University, Hangzhou 310027, China

The superconducting mechanism is not well understood for the iron pnictide LiFeP, which belongs to “111” family iron based superconductors. We have successfully synthesized LiFeP through high temperature solid state reaction. The T-dependent electrical resistivity and magnetic susceptibility indicate the superconducting transition takes place at 5 K. We report 31P nuclear magnetic resonance study in this superconducting material, including the lineshaps, spin-lattice relaxation rate 1/T1T. The Knight shift 31K is a constant for different temperature measured. The temperature dependence of spin-lattice relaxation rate 1/T1T shows a hump ~20 K, implying the enhancement of spin fluctuations, which may attribute to a SDW magnetic instability. Li off-stoicheiometry affects the ground state of Li1±δFeP and Li1±δFeAs. Efforts are under way to delicately control Li concentration and the intrinsic ground state of Li1±δFeP and Li1±δFeAs will be elucidated

67

Superconducting Properties of Ba2Ti2Fe2As4O

Yun-Lei Sun1, Abduweli Ablimit1, Jin-Ke Bao1, Hao Jiang1, Chun-Mu Feng1, Guanghan Cao1,2

1 Department of Physics, Zhejiang University, Hangzhou 310027, China 2 State Key Lab of Silicon Materials, Zhejiang University, Hangzhou 310027, China

Polycrystalline Ba2Ti2Fe2As4O has been studied through electrical resistivity, magnetic susceptibility, Hall coefficient, Seebeck coefficient and specific heat. Electrical resistivity shows that superconducting transition occurs at ~22 K. A specific-heat jump ΔC≈300 mJ/mol K corresponding to superconducting transition was also observed. Further, magnetic susceptibility under low field indicates bulk superconductivity of this compound with shielding volume fraction 90%. Magnetoresistance gives an upper critical field Hc2(0)~35 T and a coherence length ξGL(0)~ 31 Å. The negative value of Hall coefficient and Seebeck coefficient indicate that electron carriers are dominant, consistent with the result of theoretical calculation that electrons transfer from Ti to Fe. Single crystals of Ba2Ti2Fe2As4O have been grown successfully via a Ba2As3-flux method. Bulk superconductivity with Tc∼21.5 K was demonstrated in resistivity and magnetic susceptibility measurements after the as-grown crystals were annealed at 500◦C in vacuum for one week. Energy-dispersive x-ray spectra indicate that partial Ti/Fe substitution exists in the [Fe2As2] layers and the annealing process redistributes the Ti within the Fe-plane. The ordered Fe-plane stabilized by annealing exhibits superconductivity with magnetic vortex pinned by Ti. References [1] Yun-Lei Sun etc., Journal of the American Chemical Society, 134, 12893 (2012)

68

Looking for Fulde-Ferrell-Larkin-Ovchinnikov States in

Fermi-Fermi Mixtures

Jibiao Wang and Qijin Chen

Department of Physics and Zhejiang Institute of Modern Physics, Zhejiang University, China

Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states have been of great interest in the study of population imbalanced atomic Fermi gases. It has been known that the phase space of FFLO states for an equal-mass Fermi gas in three dimensions (3D) is rather small and thus has not been observed experimentally. Here we discuss these states in a homogeneous 6Li–40K mixture, as well as for other mass ratios, as they undergo the BCS–BEC crossover, using a pairing fluctuation theory. We find that when 40K is majority, a stable FFLO phase persists throughout the BCS through BEC regimes, with the population imbalances evolving from small to large. In contrast, when 6Li is the majority, a stable FFLO phase exists only in the BCS regime. We also find that the phase space of stable FFLO states becomes substantially larger as the mass ratio increases at unitarity. This should make it easier to detect such states in experiments.

69

Single Crystal Growth, Crystal Structure and Properties of UFeGa5

Donghua Xie1, Qiuyun Chen1, Lizhu Luo1, Yanzhi Zhang2,

Qingying Xu1, Xinchun Lai1

1 Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang, Sichuan, China 2 China Academy of Engineering Physics, Mianyang, Sichuan, China

High-quality single crystals of UFeGa5 were successfully grown with the Ga-flux method. The single crystal structure has been studied by X-ray diffraction technique and Rietveld method. The electrical resistivity and specific heat were measured. The results show that the structure of as-grown UFeGa5 single crystal is in good order and its’ crystallinity property is well. The UFeGa5 has the HoCoGa5 type-structure with space group P4/mmm (No.123). The lattice constants of a and c are 0.42533(2) nm, c= 0.67298(3) nm, respectively, and the crystal structure were confirmed by transmission electron microscopy. The low temperature resistivity follows Fermi liquid nature and the electronic specific heat coefficient is 10 mJ/mol·K2.

70

Sr and Mn Co-doped LaCuSO: A Wide Band Gap Oxide Diluted

Magnetic Semiconductor with TC around 200 K

Xiaojun Yang


Owing to potential application in the field of spintronics, Diluted Magnetic Semiconductors (DMS) have attracted much interest. Limited by the chemical solubility, traditional III-V based DMS systems, such as (Ga,Mn)As, are chemically metastable, and are available only as thin films. Therefore, the bulk DMS materials are highly required to obtain more reliable results. Available of bulk crystalline specimens make it possible for μSR, NMR and even neutron scattering. Recently, I-II-V based Li(Zn,Mn)As was theoretically proposed and experimentally synthesized as a bulk DMS material with Curie temperature (TC) of 50 K. Here we report the synthesis of a bulk oxide diluted magnetic semiconductor (DMS) system La1-xSrxCu0.925Mn0.075SO (x = 0, 0.025, 0.05, 0.075 and 0.1) with tetragonal ZrCuSiAs (1111) structure. As a wide band gap p-type oxide semiconductor, LaCuSO satisfies all the conditions forecasted theoretically to be a room temperature DMS. The Curie temperature (TC) is around 200 K as x ≥ 0.05, which is among the highest TC record of known bulk DMS materials up to now. The system provides a rare example of oxide DMS system with p-type conduction, which is important for formation of high temperature spintronic devices.

71

Superconducting Properties of the Skutterudite Superconductor

LaPt4Ge12 Probed by Penetration Depth Experiments and μSR

Jinglei Zhang

Center for Correlated Matter and Department of Physics, Zhejiang University

We report on a study of the superconducting properties for high quality LaPt4Ge12 samples by means of tunnel diode oscillator (TDO) technique and transverse field (TF) muon-spin rotation (μSR). At low temperature (T<<Tc),¸ λ(T) increases exponentially with temperature, strongly suggesting the superconducting gap is fully opened. The superfluid density derived from¸ λ(T) exhibits unusually long suppression near Tc which is not observed in μSR data. We find ρsTDO could be well-fitted by two band γ-model. The difference of the superfluid density deduced from two techniques might be a consequence of multiband superconductivity in this compound. * Collaboration with L. Jiao, Y. Chen, Z. F. Weng, C. Y. Guo, and H. Q. Yuan, M. Nicklas, R.

Gumeniuk, W. Schnelle, A. Leithe-Jasper, Y. Grin, F. Steglich, A. Maisuradze, C. Baines, R.

Khasanov, A. Amato.

72

STM and ARPES Study of the Heavy-fermion Compound CeIn3

Yun Zhang, Donghua Xie, Wei Feng, Qiuyun Chen, Shiyong Tan, Xiegang Zhu, Xinchun Lai

Science and Technology on Surface Physics and Chemistry Laboratory, Mianyang, Sichuan, China

The interaction of the f magnetic moment and the conduction electron in heavy-fermion

compounds leads to abundant groud states with a heavy effective mass at low temperature, such as

the superconductivity, non-fermi-liquid behaviors. Here we used Scanning Tunneling Microscope

(STM) to detect the (100) surface of the cubic structure CeIn3 and the Scanning Tunneling

Spectroscopy (STS) investigation was also performed. We demonstrate the interatomic distance of

CeIn3 from the atom tip corresponds to the XRD result and the STS spectrum related to the

surface density of the energy states accords with the UPS measurement, three characteristic peaks

existing near the fermi energy. The characteristic of the 4f electron from the UPS measurement is

different from other Ce compound. A big energy shift is found about the f electron around -1.3eV

related to fermi energy. But the tail-like f1 feature can’t be found with a photon energy 21.2eV at

77K, indicating the nearly local nature of 4f electrons. Angle Resolved Photoemission

Spectroscopy (ARPES) was also used to measure the energy band structure and Fermi surface

structure. A strong spin-orbit coupling effect is found, namely the Rashba effect.

73

Superconductivity and Density Wave in BaTi2(Sb1−xBix)2O and

Physical Properties of New Material (EuF)2Ti2Pn2O

Huifei Zhai


We have performed an isovalent substitution study in a layered titanium oxypnictide system BaTi2(Sb1−xBix)2O by the measurements of x-ray diffraction, electrical resistivity and magnetic susceptibility. The parent compound BaTi2Sb2O is confirmed to exhibit superconductivity at 1.5 K as well as charge- or spin-density wave (CDW/SDW) ordering below 55 K. With the partial substitution of Sb by Bi, the lattice parameters a, c and c/a all increase monotonically, indicating a negative chemical pressure and lattice distortion for the (super)conducting Ti2Sb2O-layers. The Bi doping elevates the superconducting transition temperature to its maximum Tc=3.7 K at x =0.17, and then Tc decreases gradually with further Bi doping. A metal-to-nonmetal transition takes place around x=0.3, and superconductivity at _1 K survives at the nonmetal side. The CDW/SDW anomaly, in comparison, is rapidly suppressed by the Bi doping, and vanishes for x _0.17. The results are discussed in terms of negative chemical pressure and disorder effect.

We synthesize new compounds of (EuF)2Ti2Pn2O (Pn=As,Sb,Bi) and study these properties by the measurements of x-ray diffraction, electrical resistivity and magnetic susceptibility.

74

List of Participants

45 Invited Speakers

Wei Bao（鲍威）

Department of Physics, Renmin University of China

Beijing 100872, China

Email: [email protected]

Xian-Hui Chen（陈仙辉）

Department of Physics, University of Science and Technology of China

96 Jinzai Road, Hefei, Anhui 230026, China


Jian-Hui Dai（戴建辉）

Hangzhou Normal University

Hangzhou 310036, China


Xi Dai（戴希）

Institute of Physics, Chinese Academy of Sciences



Claudia Felser


Noethnitzer Str. 40, 01187 Dresden, Germany


Zachary Fisk

University of California, Irvine

2186 Frederick Reines Hall, Irvine, CA 92697, USA


Edmund Gerstner

Executive Editor, China, Nature Communications


Laura H. Greene

Department of Physics, University of Illinois at Urbana-Champaign

1110 West Green Street, Urbana, IL 61801-3080, USA


Malte Grosche

Cavendish Laboratory, University of Cambridge

Madingley Road, Cambridge CB3 0HE, UK

Email: [email protected] 75

Chang-Qing Jin（靳常青）




Kazushi Kanoda

Department of Applied Physics, University of Tokyo

Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan


Stefan Kirchner

Max Planck Institute for Physics of Complex Systems

Noethnitzer Strae 38, D-01187, Dresden, Germany


Thilo Kopp

Center for Electronic Correlations and Magnetism, University of Augsburg

D-86135 Augsburg, Germany


Cornelius Krellner

Johann Wolfgang Goethe-University, Frankfurt

Max-von-Laue-Straße 1, D-60438 Frankfurt/Main, Germany


Michael Lang




Shi-Yan Li（李世燕）

Department of Physics, Fudan University

Shanghai 200433, China


Yuan Li（李源）

School of Physics, Peking University



Alois Loidl

EKM, University of Augsburg

Universitätsstrasse 1, 86159 Augsburg, Germany


76

Hilbert v. Loehneysen

Kalsruhe Institute of Technology

Wolfgang-Gaede-Str. 1, D-76131 Karlsruhe, Germany


Xin Lu（路欣）

Center for Correlated Matter, Zhejiang University



Jian-Lin Luo（雒建林）




Yuji Matsuda

Department of Physics, Kyoto University

Kyoto 606-8502, Japan


Jens Mueller




Michael Nichlas

Max-Planck-Institute for Chemical Physics of Solids

Nöthnitzer Str. 40, D-01187 Dresden, Germany


Tuson Park

Department of physics, Sungkyunkwan University

Chunchun-dong, Jangan-gu, Suwon 440-746, Korea


Qimiao Si（斯其苗）

Department of Physics and Astronomy, Rice University

6100 Main Street, Houston, Texas 77005, USA


Frank Steglich


Nothnitzer Str. 40, D-01187 Dresden, Germany


77

Oliver Stokert

Max-Planck-Institute for Chemical Physics of Solids

Noethnitzer Str. 40, D-01187 Dresden, Germany


Pei-Jie Sun（孙培杰）




Liu Hao Tjeng




Roser Valenti




Nan-Ling Wang（王楠林）




Qiang-Hua Wang（王强华）

Department of Physics, Nanjing University

Nanjing 210093, China


Yu-Peng Wang（王玉鹏）




Hai-Hu Wen（闻海虎）

Department of Physics, Nanjing University

Nanjing 210093, China


Zheng-Yu Weng（翁征宇）

Institute for Advanced Study, Tsinghua University



78

Steffen Wirth




Joachim Wosnitza

Hochfeld-Magnetlabor Dresden

Postfach 510119, 01314 Dresden, Germany


Tao Xiang（向涛）




Yi-Feng Yang（杨义峰）




Hui-Qiu Yuan（袁辉球）

Center for Correlated Matter and Department of Physics, Zhejiang University



Fuchun Zhang（张富春）

Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong, or



Guang-Ming Zhang（张广铭）

Department of Physics, Tsinghua University

HaiDian District, Beijing 100084, China


Xing-Jiang Zhou（周兴江）




Yi Zhou（周毅）

Zhejiang Institute of Modern Physics and Department of Physics, Zhejiang University

38 Zheda Road, Hangzhou, Zhejiang 310027, China


79

Other Participants

Name Email From Note

1. Chung-Hou Chung [email protected] National Chiao-Tung University

2. Fei Chen [email protected] University of Science and Technology of China

3. Xin-Chun Lai [email protected] China Academy of Engineering Physics

4. Dong-Hua Xie [email protected] China Academy of Engineering Physics Poster

5. Wei Feng [email protected] China Academy of Engineering Physics

6. Yun Zhang [email protected] China Academy of Engineering Physics Poster

7. Yu-Zhong Zhang [email protected] Tongji University

8. Zheng-Cai Xia [email protected] Huazhong University of Science and Technology

9. Zhao Jin [email protected] Huazhong University of Science and Technology

10. Ming Yang [email protected] Huazhong University of Science and Technology

11. Xi-Yu Zhu [email protected] Nanjing University

12. Sheng Li Nanjing University

13. Jian-Zhong Liu Nanjing University Poster

14. De-Long Fang Nanjing University Poster

15. Chao Cao [email protected] Hangzhou Normal University

16. Bin Chen [email protected] Hangzhou Normal University

17. Jin-Hu Yang [email protected] Hangzhou Normal University

80


18. Yang Guo [email protected] Hangzhou Normal University

19. Hong-Min Jiang [email protected] Hangzhou Normal University

20. Yu-Ke Li [email protected] Hangzhou Normal University

21. Xiao-Yong Feng [email protected] Hangzhou Normal University

22. Xiao-Feng Xu [email protected] Hangzhou Normal University

23. Quan-Li Ye [email protected] Hangzhou Normal University

24. Guang-Han Cao [email protected] Zhejiang University

25. Qi-Jin Chen [email protected] Zhejiang University

26. Qing-Hu Chen [email protected] Zhejiang University Poster

27. Fan-Long Ning [email protected] Zhejiang University

28. Ming-Qiu Tan [email protected] Zhejiang University

29. Zong-Li Wang [email protected] Zhejiang University

30. Zhu-an Xu [email protected] Zhejiang University

31. Yi Yin [email protected] Zhejiang University

32. Yan-Ming Che [email protected] Zhejiang University Poster

33. Cui Ding [email protected] Zhejiang University Poster

34. Hui-Yuan Man [email protected] Zhejiang University Poster

35. Fei Qi [email protected] Zhejiang University Poster

36. Yun-Lei Sun [email protected] Zhejiang University Poster

37. Ji-Biao Wang [email protected] Zhejiang University Poster

81


38. Xiao-Jun Yang [email protected] Zhejiang University Poster

39. Hui-Fei Zhai [email protected] Zhejiang University Poster

40. Abduweli Ablimit [email protected] Zhejiang University

41. Jin-Ke Bao [email protected] Zhejiang University

42. Hua Chen [email protected] Zhejiang University

43. Qian Chen [email protected] Zhejiang University

44. Jian Chen [email protected] Zhejiang University

45. Long-Chao Deng [email protected] Zhejiang University

46. Dong-Hui Xu [email protected] Zhejiang University

47. Ying Fei [email protected] Zhejiang University

48. Gong Xin [email protected] Zhejiang University

49. Sheng-Li Guo [email protected] Zhejiang University

50. Wei Guo [email protected] Zhejiang University

51. Yang He [email protected] Zhejiang University

52. Yan-Liang Hou [email protected] Zhejiang University

53. Lun-Hui Hu [email protected] Zhejiang University

54. Lei-Feng Zhang [email protected] Zhejiang University

55. Li Liu [email protected] Zhejiang University

56. Jian-Jian Miao [email protected] Zhejiang University

57. Quan Wang [email protected] Zhejiang University

82


58. Hao Wu [email protected] Zhejiang University

59. Xu-Chu Huang [email protected] Zhejiang University

60. Yu-Peng Li [email protected] Zhejiang University

61. Chuan-Yu Zhao [email protected] Zhejiang University

62. Chen-Chao Xu [email protected] Zhejiang University

63. Lin Jiao Zhejiang University Poster, V

64. Tian Shang Zhejiang University Volunteer

65. Jing-Lei Zhang Zhejiang University Poster, V

66. Ye Chen Zhejiang University Volunteer

67. Yu-Hang Chen Zhejiang University Volunteer

68. Zong-Fa Weng Zhejiang University Volunteer

69. Wen-Bing Jiang Zhejiang University Volunteer

70. Gui-Ming Pang Zhejiang University Volunteer

71. Fei Gao Zhejiang University Volunteer

72. Chun-Yu Guo Zhejiang University Volunteer

73. Teng-Fei Zhu Zhejiang University Volunteer

74. Bin Shen Zhejiang University Volunteer

75. Yi-Sheng Fang Zhejiang University Volunteer

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