Regensburg 2022 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 26: Focus Session: Topological Devices (joint session TT/KFM)

KFM 26.8: Vortrag

Donnerstag, 8. September 2022, 18:15–18:30, H10

Kondo interactions of quantum spin Hall edge channels with charge puddles — •Christopher Fuchs1,2, Pragya Shekhar1,2, Saquib Shamim1,2, Lena Fürst1,2, Johannes Kleinlein1,2, Jukka I. Väyrynen3, Hartmut Buhmann1,2, and Laurens W. Molenkamp1,21Physikalisches Institut, Universität Würzburg, Würzburg, Germany — 2Institute for Topological Insulators, Universität Würzburg, Würzburg, Germany — 3Department of Physics and Astronomy, Purdue University, West Lafayette, USA

Quantum spin Hall edge channels are protected against backscattering by time-reversal symmetry. However, since the first observation of the quantum spin Hall effect in HgTe in 2007 it is known that reproducible fluctuations shape the quantization plateau when the chemical potential is tuned through the bulk gap. Here, those fluctuations are examined in high-quality micron-sized quantum well structures of HgTe at millikelvin temperatures. By performing temperature and gate-dependent measurements, we conclude that the observed conductance fluctuations indicate interactions of the edge channel electrons with individual charge puddles -- microscopic fluctuations in the potential landscape commonly observed in narrow gap semiconductors -- that act like Kondo correlated quantum dots. The resulting spin-flip backscattering gives rise to a distinct Kondo-like temperature dependence of the conductance fluctuations, which is backed up by theoretical modelling. Our results provide insight into the leading mechanism of decoherence of quantum spin Hall edge channels.

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