Superconducting proximity effect in InAsSb surface quantum wells with in-situ Al contact

TL;DR

This study demonstrates a strong superconducting proximity effect in InAsSb quantum wells with epitaxial Al, highlighting their potential for topological quantum computing due to enhanced spin-orbit coupling and high interface quality.

Contribution

First demonstration of robust superconducting proximity effect in epitaxial InAsSb quantum wells with Al contacts, showing promising properties for topological superconductivity.

Findings

High-quality interfaces observed in InAsSb/Al heterostructures.

Strong proximity effect evidenced by high I_c R_N and I_ex R_N values.

Long-range, highly-transparent contacts suitable for quantum applications.

Abstract

We demonstrate robust superconducting proximity effect in InAs$_{0.5}$Sb$_{0.5}$ quantum wells grown with epitaxial Al contact, which has important implications for mesoscopic and topological superconductivity. Unlike more commonly studied InAs and InSb semiconductors, bulk InAs$_{0.5}$Sb$_{0.5}$ supports stronger spin-orbit coupling and larger $g$-factor. However, these potentially desirable properties have not been previously measured in epitaxial heterostructures with superconductors, which could serve as a platform for fault-tolerant topological quantum computing. Through structural and transport characterization we observe high-quality interfaces and strong spin-orbit coupling. We fabricate Josephson junctions based on InAs$_{0.5}$Sb$_{0.5}$ quantum wells and observe strong proximity effect. These junctions exhibit product of normal resistance and critical current, $I_{c}R_{N} = \SI{270}{\micro V}$, and excess current, $I_{ex}R_{N} = \SI{200}{\micro V}$ at contact separations of 500~nm. Both of these quantities demonstrate a robust and long-range proximity effect with highly-transparent contacts.