Effect of the iron valence in the two types of layers in LiFeO$_2$Fe$_2$Se$_2$

TL;DR

This study investigates how the different iron valences in LiFeO$_2$Fe$_2$Se$_2$ influence its electronic and magnetic properties, revealing that local correlations suppress the 3d^5 states and restore typical superconductor characteristics.

Contribution

It provides the first detailed analysis of the impact of mixed iron valences on electronic structure and magnetism in this novel superconductor using advanced theoretical methods.

Findings

Different Fe valences lead to distinct magnetic moments.

Local correlations suppress 3d^5 contributions from LiFeO$_2$ layer.

Restoration of standard iron-based superconductor electronic structure.

Abstract

We perform electronic structure calculations for the recently synthesized iron-based superconductor LiFeO$_2$Fe$_2$Se$_2$. In contrast to other iron-based superconductors, this material comprises two different iron atoms in 3$d^5$ and 3$d^6$ configurations. In band theory, both contribute to the low-energy electronic structure. Spin-polarized density functional theory calculations predict an antiferromagnetic metallic ground state with different moments on the two Fe sites. However, several other almost degenerate magnetic configurations exist. Due to their different valences, the two iron atoms behave very differently when local quantum correlations are included through the dynamical mean-field theory. The contributions from the half-filled 3$d^5$ atoms in the LiFeO$_2$ layer are suppressed and the 3$d^6$ states from the FeSe layer restore the standard iron-based superconductor fermiology.