Fate of $yz$/$zx$ orbital degeneracy and $xy$ Fermi surface in Ru substituted FeSe$_{1-x}$Te$_{x}$

TL;DR

This study uses ARPES to examine how Ru substitution affects the electronic structure of FeSe$_{1-x}$Te$_x$, revealing suppression of the $xy$ Fermi surface and partial recovery of $yz$/$zx$ band degeneracy, indicating coexistence of nematic states.

Contribution

It provides new insights into how Ru substitution influences orbital degeneracy and electronic nematicity in FeSe$_{1-x}$Te$_x$ superconductors.

Findings

Suppression of the $xy$ Fermi surface with Ru substitution.

Partial recovery of $yz$/$zx$ band degeneracy.

Spectral broadening near zone boundaries due to lattice disorder.

Abstract

We have investigated the impact of Ru substitution on the multi-band electronic structure of FeSe$_{1-x}$Te$_x$ by means of angle-resolved photoemission spectroscopy (ARPES). The ARPES results exhibit suppression of the $xy$ Fermi surface and the spectral broadening near the zone boundaries, which can be associated with the lattice disorder introduced by the Ru substitution. The degeneracy of the Fe 3$d$ $yz$/$zx$ bands at the zone center, which is broken in FeSe$_{1-x}$Te$_x$, is partly recovered with the Ru substitution, indicating coexistence of nematic and non-nematic electronic states.