Accurate modeling of FeSe with screened Fock exchange and Hund's metal correlations

TL;DR

This paper presents an ab initio approach that accurately models FeSe's electronic properties by incorporating screened Fock exchange and Hund's correlations, successfully reproducing experimental observations and temperature-dependent behaviors.

Contribution

It introduces a novel ab initio framework that captures FeSe's electronic structure and thermoelectric properties within the Hund's metal phase, improving upon previous models.

Findings

Accurately reproduces FeSe's band structure and Fermi surface features.

Matches experimental interband optical spectra.

Qualitatively captures temperature dependence of thermoelectric power.

Abstract

We reproduce the electronic properties of FeSe in the high-temperature phase within an ab initio framework that includes screened Fock exchange and local dynamical correlations. We robustly capture the experimental band structure, as long as the system is in the Hund's metal phase. In particular, we account for the shrinking of the Fermi pockets and the sinking below the Fermi level of the hole pocket with $xy$ orbital character. This entails the elusive correct estimate of the Sommerfeld coefficient, and supports the interpretation of non-compensated Fermi pockets seen in ARPES in terms of surface electron doping. More stringently, our modeling matches well the experimental interband optical spectrum, and captures qualitatively the temperature dependence of the thermoelectric power, extremely sensitive to the details of the bands around the Fermi level.