Proximity-induced superconductivity within the InAs/GaSb edge conducting state

TL;DR

This study demonstrates proximity-induced superconductivity in the edge states of InAs/GaSb bilayers, revealing different behaviors depending on quantum well thickness and providing evidence for edge state superconductivity.

Contribution

It provides experimental evidence of proximity-induced superconductivity within InAs/GaSb edge states across different quantum well thicknesses.

Findings

Standard Andreev reflection in 10 nm samples.

Proximity-induced superconductivity in 12 nm and 14 nm samples.

Observation of mesoscopic resistance fluctuations in 14 nm samples.

Abstract

We experimentally investigate Andreev transport through the interface between an indium superconductor and the edge of the InAs/GaSb bilayer. To cover all possible regimes of InAs/GaSb spectrum, we study samples with 10 nm, 12 nm, and 14 nm thick InAs quantum wells. For the trivial case of a direct band insulator in 10~nm samples, differential resistance demonstrates standard Andreev reflection. For InAs/GaSb structures with band inversion (12~nm and 14 nm samples), we observe distinct low-energy structures, which we regard as direct evidence for the proximity-induced superconductivity within the current-carrying edge state. For 14~nm InAs well samples, we additionally observe mesoscopic-like resistance fluctuations, which are subjected to threshold suppression in low magnetic fields.