Florian Bauer(1,2), Jan Heyder(1,2), Enrico Schubert(1), David Borowsky(1), Daniela Taubert(1), Benedikt Bruognolo(1,2), Dieter Schuh(3), Werner Wegscheider(4), Jan von Delft(1,2), Stefan Ludwig(1)[1] Center for NanoScience and Fakultät für Physik, Ludwig-Maximilians-Universität München[2] Arnold Sommerfeld Center for Theoretical Physics, Ludwig-Maximilians-Universität München[3] Institut für Angewandte Physik, Universität Regensburg[4] Laboratory for Solid State Physics, ETH ZürichJournal Club @ InFis – UFUGerson J. Ferreiragersonjferreira@infis.ufu.br

21/02/2014

Microscopic origin of the 0.7-anomaly“ ”in quantum point contactsNature 501, 73 (2013)

Odd and even Kondo effects from emergent localization in QPCsIqbal, Levy, Koop, Dekker, de Jong, van der Velde, Reuter, Wieck, Aguado, Meir, van der WalNature 501, 79 (2013)

What lurks below the last plateau: experimental studies of the 0.7 × 2e2/h conductance anomaly in one-dimensional systemsTOPICAL REVIEW

A. P. Micolich, School of Physics, University of New South Wales, Sydney, AustraliaJ. Phys.: Condens. Matter 23 (2011) 443201

[Thomas, Nicholls, Simmons, Pepper, Mace, Ritchie, PRL 77, 135 (1996)]~ 18 years old!!!

✗ Spontaneus spin polarization✗ Kondo effect✗ Luttinger Liquid✗ Phenomenological spin-gap✗ Subband pinning✗ e-phonon interaction✗ …

News & Views:QPC: Double or nothing? A. P. Micolich, Nature Physics 9, 530 (2013)

[Cronenwett, Lynch, Goldhaber-Gordon, Kouwenhoven, Marcus, Hirose, Wingreen, Umansky, PRL 88, 226805 (2002)]

The non-interacting picture2DEG 2DEGQPC/wire

xy

QPC as an infinite wire

Conductance via Landauer

Coupling to the leads:[Büttiker, PRB 41, 7906 (1990)]

Increasingtemperature

Increasingmagnetic field

11/23/2

2DEG 2DEGQPC/wire

Microscopic origin of the 0.7-anomaly in quantum point contacts“ ” Nature 501, 73 (2013)

SOPT: second order perturbation theory (Hartree and Fock diagrams)fRG: functional renormalization group

LDOS

jvan Hove singularity

LDOSCharge densityMagnetizationSpin susceptibilityFriedel oscillations

VG

FRG

V

SOPT Experiment

V

Low temperature, increasing B

Increasingmagnetic fieldNon-interacting

+Diamagnetic shift

ExperimentSOPTB = 0, increasing temperature

IncreasingtemperatureCheck papers fromTobias Micklitz(CBPF)

Zero bias (anomalous) peakExperiment SOPT

Predictions from SOPTTobias Micklitz(CBPF) ZBP

Is the mystery solved?- Fixed conductance point below 0.5- Zero bias peak without Kondo- what about the high bias regime?- new Friedel oscillations and the length dependence?

the actual 0.7 plateau is not there!!