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 26.1: Hauptvortrag

Donnerstag, 8. September 2022, 15:00–15:30, H10

Supercurrents in HgTe-based topological nanowires — •Dieter Weiss — Institute for Experimental and Applied Physics, University of Regensburg, 93040 Regensburg/Germany

Topological insulator (TI) nanowires in proximity to conventional superconductors constitute a tunable platform to realize topological superconductivity and Majorana zero modes [1]. Tuning is done by an axial magnetic flux φ transforming the system from trivial at φ=0 to topologically nontrivial when a magnetic flux quantum φ0=h/2e threads the wire’s cross-section. Here, we investigate the evolution of the supercurrent in ballistic HgTe Josephson junctions as a function of axial magnetic flux φ and examine the periodicity of the supercurrent utilizing microwave irradiation and probing Shapiro steps. Suppressed odd Shapiro steps herald the existence of 4π-periodic supercurrents, a signature of topological superconductivity. Our data suggest that at small φ this 4π-periodic supercurrent is of trivial origin but that at magnetic fields above φ0/2, topological 4π-periodic supercurrents take over [2].

Work done in cooperation with Ralf Fischer, Wolfgang Himmler, Johannes Ziegler, Jordi Picó-Cortés , Gloria Platero, Milena Grifoni, Dmitriy A. Kozlov, N. N. Mikhailov, Sergey A. Dvoretsky , Michael Barth, Jakob Fuchs, Cosimo Gorini, Klaus Richter, and Christoph Strunk.

[1] A. Cook and M. Franz, PRB 84, 201105(R) (2011)

[2] R. Fischer et al., PRR 4, 013087 (2022)

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