<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>4</mml:mn><mml:mi>π</mml:mi></mml:mrow></mml:math>-periodic supercurrent tuned by an axial magnetic flux in topological insulator nanowires
R. Fischer, Jordi Picó-Cortés, Wolfgang Himmler, Gloria Platero, Milena Grifoni, Dmitriy A. Kozlov, Н. Н. Михайлов, S. A. Dvoretsky, Christoph Strunk, Dieter Weiss
Abstract
Topological insulator (TI) nanowires in proximity to conventional superconductors have been proposed as a tunable platform to realize topological superconductivity and Majorana zero modes. The tuning is done using an axial magnetic flux $\ensuremath{\phi}$ which allows transforming the system from trivial at $\ensuremath{\phi}=0$ to topologically nontrivial when half a magnetic flux quantum ${\ensuremath{\phi}}_{0}/2$ threads the cross-section of the wire. Here, we explore the expected topological transition in TI-wire-based Josephson junctions as a function of magnetic flux by probing the $4\ensuremath{\pi}$-periodic fraction of the supercurrent, which is considered an indicator of topological superconductivity. Our data suggest that this $4\ensuremath{\pi}$-periodic supercurrent is at lower magnetic field largely of trivial origin but that, at magnetic fields above $\ensuremath{\sim}{\ensuremath{\phi}}_{0}/4$, topological $4\ensuremath{\pi}$-periodic supercurrents take over.