Multiple Andreev reflections in topological insulator nanoribbons

TL;DR

This paper reports the fabrication and measurement of topological insulator nanoribbon Josephson junctions, revealing high interface transparency, multiple Andreev reflections, and surface states, advancing the study of topological superconductivity.

Contribution

It demonstrates highly transparent superconducting contacts and multiple Andreev reflections in TI nanoribbon Josephson junctions, providing a platform for topological superconductivity research.

Findings

Observation of supercurrent in TI nanoribbon JJs

High interface transparency with $ au$ = 0.83

Detection of multiple Andreev reflections

Abstract

Superconducting proximity junctions made of topological insulator (TI) nanoribbons (NRs) provide a useful platform for studying topological superconductivity. We report on the fabrication and measurement of Josephson junctions (JJs) using Sb doped Bi$_2$Se$_3$ NRs in contact with Al electrodes. Aharonov$-$Bohm and Altshuler$-$Aronov$-$Spivak oscillations of the axial magneto-conductance of TI NR were observed, indicating the existence of metallic surface states along the circumference of the TI NR. We observed the supercurrent in the TI NR JJ and subharmonic gap structures of the differential conductance due to multiple Andreev reflections. The interface transparency of the TI NR JJs estimated based on the excess current reaches $\tau$ = 0.83, which is among the highest values reported for TI JJs. The temperature dependence of critical current is consistent with the short and ballistic junction model confirming the formation of highly transparent superconducting contacts on the TI NR. Our observations would be useful for exploring topological Josephson effects in TI NRs.