Allotropic transition of Dirac semimetal {\alpha}-Sn to superconductor {\beta}-Sn induced by irradiation of focused ion beam

TL;DR

This study demonstrates that focused ion beam irradiation can induce a phase transition in { extalpha}-Sn from a topological Dirac semimetal to a superconducting allotrope, opening new avenues for fabricating heterostructures.

Contribution

It reveals that local annealing from FIB irradiation causes { extalpha}-Sn to transform into superconducting { extbeta}-Sn, providing a novel method for creating TDS/superconductor heterostructures.

Findings

FIB irradiation induces { extalpha}-Sn to transform into { extbeta}-Sn.

XPS indicates chemical state changes due to crystal structure differences.

Transformation mechanism linked to local annealing effects.

Abstract

Diamond-type structure allotrope {\alpha}-Sn is attracting much attention as a topological Dirac semimetal (TDS). In this study, we demonstrate that {\alpha}-Sn undergoes a phase transition to another allotrope {\beta}-Sn with superconductivity at low temperature by irradiating with a focused Ga ion beam (FIB). To clarify the transition mechanism, we performed X-ray photoemission spectroscopy (XPS) measurements on an {\alpha}-Sn thin film irradiated with FIB and an as-grown {\alpha}-Sn thin film. The XPS results suggest that the local annealing, which is one of the side effects of FIB, causes the transformation from {\alpha}-Sn into {\beta}-Sn. Furthermore, the difference in the chemical states between {\alpha}-Sn and {\beta}-Sn can be quantitatively explained by the crystal structures rather than the degree of metallicity reflecting the conductivity. These results propose a new way of fabricating TDS/superconductor in-plane heterostructures based on {\alpha}-Sn and {\beta}-Sn.