Engineering Hybrid Epitaxial InAsSb/Al Nanowire Materials for Stronger Topological Protection

TL;DR

This paper reports on the growth and characterization of hybrid InAsSb/Al nanowires, demonstrating enhanced spin-orbit coupling and topological properties, with implications for topological quantum computing.

Contribution

It introduces a method to grow hybrid InAsSb/Al nanowires with optimized composition and structure, showing improved spin-orbit interaction and potential for stronger topological protection.

Findings

Strongest spin-orbit interaction at intermediate compositions

Epitaxial InAsSb/Al interfaces enable hard superconducting gaps

Evidence of topological phase transitions at low magnetic fields

Abstract

The combination of strong spin-orbit coupling, large $g$-factors, and the coupling to a superconductor can be used to create a topologically protected state in a semiconductor nanowire. Here we report on growth and characterization of hybrid epitaxial InAsSb/Al nanowires, with varying composition and crystal structure. We find the strongest spin-orbit interaction at intermediate compositions in zincblende InAs$_{1-x}$Sb$_{x}$ nanowires, exceeding that of both InAs and InSb materials, confirming recent theoretical studies \cite{winkler2016topological}. We show that the epitaxial InAsSb/Al interfaces allows for a hard induced superconducting gap and 2$e$ transport in Coulomb charging experiments, similar to experiments on InAs/Al and InSb/Al materials, and find measurements consistent with topological phase transitions at low magnetic fields due to large effective $g$-factors. Finally we present a method to grow pure wurtzite InAsSb nanowires which are predicted to exhibit even stronger spin-orbit coupling than the zincblende structure.