Selective Area Superconductor Epitaxy to Ballistic Semiconductor Nanowires

TL;DR

This paper introduces a selective-area epitaxy technique for InSb-Al nanowires that achieves a hard superconducting gap and ballistic 1D superconductivity, advancing the development of topological quantum computing devices.

Contribution

The authors develop a selective-area epitaxy method for InSb-Al nanowires that reduces disorder and enables ballistic transport, improving the quality of hybrid superconductor-semiconductor systems.

Findings

Epitaxial InSb-Al nanowires exhibit a hard superconducting gap.

Demonstration of ballistic 1D superconductivity in nanowires.

Achieved micron-scale ballistic transport in superconducting island devices.

Abstract

Semiconductor nanowires such as InAs and InSb are promising materials for studying Majorana zero-modes and demonstrating non-Abelian particle exchange relevant for topological quantum computing. While evidence for Majorana bound states in nanowires has been shown, the majority of these experiments are marked by significant disorder. In particular, the interfacial inhomogeneity between the superconductor and nanowire is strongly believed to be the main culprit for disorder and the resulting soft superconducting gap ubiquitous in tunneling studies of hybrid semiconductor-superconductor systems. Additionally, a lack of ballistic transport in nanowire systems can create bound states that mimic Majorana signatures. We resolve these problems through the development of selective-area epitaxy of Al to InSb nanowires, a technique applicable to other nanowires and superconductors. Epitaxial InSb-Al devices generically possess a hard superconducting gap and demonstrate ballistic 1D superconductivity and near perfect transmission of supercurrents in the single mode regime, requisites for engineering and controlling 1D topological superconductivity. Additionally, we demonstrate that epitaxial InSb-Al superconducting island devices, the building blocks for Majorana based quantum computing applications, prepared using selective area epitaxy can achieve micron scale ballistic 1D transport. Our results pave the way for the development of networks of ballistic superconducting electronics for quantum device applications.