Topological nature of FeSe$_{0.5}$Te$_{0.5}$ superconductor

TL;DR

This study reveals that FeSe$_{0.5}$Te$_{0.5}$ is a topologically non-trivial superconductor with Dirac surface states, induced by Te substitution, which may host non-trivial superconducting channels on its surface.

Contribution

First-principles calculations and ARPES measurements demonstrate the topological nature of FeSe$_{0.5}$Te$_{0.5}$, highlighting the role of Te in inducing band inversion and Dirac surface states.

Findings

FeSe$_{0.5}$Te$_{0.5}$ has a non-trivial topological electronic structure.

Te substitution induces band inversion at the Z point.

Surface states exhibit Dirac cone characteristics.

Abstract

We demonstrate, using first-principles calculations, that the electronic structure of FeSe$_{1-x}$Te$_{x}$ ($x$=0.5) is topologically non-trivial, characterized by an odd $\mathbb Z_2$ invariant and Dirac cone type surface states, in sharp contrast to the end member FeSe ($x$=0). This topological state is induced by the enhanced three-dimensionality and spin-orbit coupling due to Te substitution (compared to FeSe), characterized by a band inversion at the $Z$ point of the Brillouin zone, which is confirmed by our ARPES measurements. The results suggest that the surface of FeSe$_{0.5}$Te$_{0.5}$ may support a non-trivial superconducting channel in proximity to the bulk.