Spin-orbit interaction and induced superconductivity in an one-dimensional hole gas

TL;DR

This paper investigates germanium-silicon nanowires with strong spin-orbit interaction and induced superconductivity, highlighting their potential for topological quantum computing by demonstrating a hard superconducting gap and one-dimensional transport properties.

Contribution

It provides experimental evidence of one-dimensional hole gas behavior, anisotropic g-factors, and a hard superconducting gap in Ge-Si nanowires, advancing their use in topological superconductor research.

Findings

Two transport channels indicating one-dimensionality

Evidence of direct Rashba spin-orbit interaction

Observation of a hard superconducting gap

Abstract

Low dimensional semiconducting structures with strong spin-orbit interaction (SOI) and induced superconductivity attracted much interest in the search for topological superconductors. Both the strong SOI and hard superconducting gap are directly related to the topological protection of the predicted Majorana bound states. Here we explore the one-dimensional hole gas in germanium silicon (Ge-Si) core-shell nanowires (NWs) as a new material candidate for creating a topological superconductor. Fitting multiple Andreev reflection measurements shows that the NW has two transport channels only, underlining its one-dimensionality. Furthermore, we find anisotropy of the Lande g-factor, that, combined with band structure calculations, provides us qualitative evidence for direct Rashba SOI and a strong orbital effect of the magnetic field. Finally, a hard superconducting gap is found in the tunneling regime, and the open regime, where we use the Kondo peak as a new tool to gauge the quality of the superconducting gap.