Orbital Selective Mott Transition Effects and Non-Trivial Topology of Iron Chalcogenide

TL;DR

This paper investigates how strong electronic correlations and orbital selective Mott transitions influence the topological surface states in FeSe$_{1-x}$Te$_{x}$, revealing the dual role of proximity to the Mott phase in facilitating and destroying topological superconductivity.

Contribution

It connects the orbital selective Mott transition with topological surface states in iron chalcogenides using advanced theoretical methods, providing a new framework for understanding their interplay.

Findings

Topological surface states have Fe($d_{xy}$) character.

Proximity to the OSMT enhances topological surface states.

Too close to the orbital Mott phase destroys Z$_{2}$ topological superconductivity.

Abstract

The iron-based superconductor FeSe$_{1-x}$Te$_{x}$ (FST) has recently gained significant attention as a host of two distinct physical phenomena: ($i$) Majorana zero modes which can serve as potential topologically protected qubits, and ($ii$) a realization of the orbital selective Mott transition (OSMT). In this Letter, we connect these two phenomena and provide new insights into the interplay between strong electronic correlations and non-trivial topology in FST. Using linearized quasiparticle self-consistent GW plus dynamical mean-field theory, we show that the topologically protected Dirac surface state has substantial Fe($d_{xy}$) character. The proximity to the OSMT plays a dual role, it facilitates the appearance of the topological surface state by bringing the Dirac cone close to the chemical potential, but destroys the Z$_{2}$ topological superconductivity when the system is too close to the orbital selective Mott phase (OSMP). We derive a reduced effective Hamiltonian that describes the topological band. Its parameters capture all the chemical trends found in the first principles calculation. Our findings provide a framework for further study of the interplay between strong electronic correlations and non-trivial topology in other iron-based superconductors.