Epitaxially Driven Phase Selectivity of Sn in Hybrid Quantum 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 $\alpha -\mathrm{Sn}$ or superconducting $\beta -\mathrm{Sn}$. For InAs nanowires, we obtain phase-pure, superconducting $\beta -\mathrm{Sn}$ shells. However, for InSb and InAsSb nanowires, an initial epitaxial $\alpha -\mathrm{Sn}$ phase evolves into a polycrystalline shell of coexisting $\alpha$ and $\beta$ phases, where the $\beta /\alpha$ volume ratio increases with Sn shell thickness. Whether these nanowires exhibit superconductivity or not critically relies on the $\beta -\mathrm{Sn}$ 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.

12 pages, 5 figures