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

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.

8 pages, 7 figures, 3 tables