Correlation-driven topological Fermi surface transition in FeSe

TL;DR

This study uses advanced computational methods to reveal a topological Fermi surface transition in FeSe, linking it to magnetic correlation changes and potential impacts on superconductivity.

Contribution

It demonstrates a correlation-driven Lifshitz transition in FeSe and connects it to magnetic and superconducting properties, providing new insights into its electronic structure.

Findings

Fermi surface undergoes a Lifshitz transition with lattice expansion.

Magnetic correlations shift from $(\pi,\pi)$ to $(\pi,0)$.

Van Hove singularity influences superconductivity.

Abstract

The electronic structure and phase stability of paramagnetic FeSe is computed by using a combination of ab initio methods for calculating band structure and dynamical mean-field theory. Our results reveal a topological change (Lifshitz transition) of the Fermi surface upon a moderate expansion of the lattice. The Lifshitz transition is accompanied with a sharp increase of the local moments and results in an entire reconstruction of magnetic correlations from the in-plane magnetic wave vector $(\pi,\pi)$ to $(\pi,0)$. We attribute this behavior to a correlation-induced shift of the Van Hove singularity originating from the $d_{xy}$ and $d_{xz}/d_{yz}$ bands at the M-point across the Fermi level. We propose that superconductivity is strongly influenced, or even induced, by a Van Hove singularity.