Revealing intrinsic superconductivity of the Nb/BiSbTe$_2$Se interface

TL;DR

This paper demonstrates intrinsic superconductivity at the Nb/BiSbTe$_2$Se interface in Josephson junctions, revealing a second critical current due to the interface's unique properties, which impacts topological superconductivity research.

Contribution

It uncovers and analyzes the intrinsic superconductivity at the S/TI interface, a novel phenomenon relevant for topological quantum devices.

Findings

Observation of double critical current in S/TI Josephson junctions

Identification of the second critical current as intrinsic to the interface

Implications for fabrication processes involving Ar-plasma cleaning

Abstract

Typically, topological superconductivity is reachable via proximity effect by a direct deposition of superconductor (S) on top of a topological insulator (TI) surface. Here we observed and analyzed the double critical current in the Josephson junctions based on the topological insulator in the fabricated planar Superconducting Quantum Interference Device. By measuring critical currents as a function of temperature and magnetic field, we show that the second critical current stems from the intrinsic superconductivity of the S/TI interface, which is supported by the modified Resistively Shunted Junction model and Transmission Electron Microscopy studies. This complex structure of the interface should be taken into account when technological process involves Ar-plasma cleaning.