Epitaxially Driven Phase Selectivity of Sn in Hybrid Quantum Nanowires

TL;DR

This study explores how epitaxial growth conditions influence the phase of tin in hybrid nanowires, revealing how to control superconductivity and topological properties in quantum materials.

Contribution

It demonstrates the phase control of Sn in hybrid nanowires through epitaxial growth, enabling tailored superconducting and topological behaviors in quantum nanostructures.

Findings

InAs nanowires achieve phase-pure, superconducting β-Sn shells.

InSb and InAsSb nanowires develop mixed α and β phases with increasing Sn thickness.

Superconductivity depends critically on the β-Sn content in the nanowires.

Abstract

Hybrid semiconductor/superconductor nanowires constitute a pervasive platform for studying gate-tunable superconductivity and the emergence of topological behavior. Their low-dimensionality and crystal structure flexibility facilitate novel heterostructure growth and efficient material optimization; crucial prerequisites for accurately constructing complex multi-component quantum materials. Here, we present an extensive optimization of Sn growth on InSb, InAsSb and InAs nanowires. We demonstrate how the growth conditions and the crystal structure/symmetry of the semiconductor drive the formation of either semi-metallic $\mathrm{\alpha-Sn}$ or superconducting $\mathrm{\beta-Sn}$. For InAs nanowires, we obtain phase-pure, superconducting $\mathrm{\beta-Sn}$ shells. However, for InSb and InAsSb nanowires, an initial epitaxial $\mathrm{\alpha-Sn}$ phase evolves into a polycrystalline shell of coexisting $\mathrm{\alpha}$ and $\mathrm{\beta}$ phases, where the $\beta/\alpha$ volume ratio increases with Sn shell thickness. Whether these nanowires exhibit superconductivity or not critically relies on the $\mathrm{\beta-Sn}$ content. Therefore, this work provides key insights into Sn phase control on a variety of semiconductors, with consequences for the yield of superconducting hybrids suitable for generating topological systems.