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TT: Fachverband Tiefe Temperaturen

TT 3: Topology: Quantum Hall Systems

TT 3.9: Talk

Monday, March 18, 2024, 12:00–12:15, H 2053

New evidence for protected helical Andreev hinge modes in a bismuth nanoring Josephson junction — •Alexandre Bernard1, Yang Peng2, Alik Kasumov1, Richard Deblock1, Meydi Ferrier1, Franck Fortuna3, Yuval Oreg4, Felix von Oppen5, Hélène Bouchiat1, and Sophie Guéron11Laboratoire de Physique des Solides, France — 2California State University, USA — 3Institut des Sciences Moléculaires d’Orsay, France — 4Weizmann Institute of Science, Israel — 5Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Germany

Second-order topological insulators are characterized by helical, non-spin-degenerate one-dimensional states running along opposite crystal hinges with no backscattering [1]. Injecting superconducting pairs therefore entails splitting Cooper pairs into two families of helical Andreev states of opposite helicity, one at each hinge. Here we provide new evidence for such separation via the measurement and analysis of the switching supercurrent statistics of a crystalline nanoring of bismuth connected to superconducting electrodes. Using a phenomenological model of two helical Andreev hinge modes, we identify an ’odd’ state in this long junction, and we find that pairs relax at a rate comparable to individual quasiparticles, in contrast to the much faster pair relaxation of non-topological systems [2].

The nanowire was made by Alik Kasumov, Vladimir Volkov and Yusif Kasumov in Chernogolovka.

[1] F. Schindler et al., Nat. Phys. 14 (2018) 918

[2] A. Bernard et al., Nat. Phys. 19 (2023) 358

Keywords: Topological Insulator; Josephson junction; Spin-orbit; Helical current; Switching statistics

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