Interplay of nematic and magnetic orders in FeSe under pressure

TL;DR

This paper explains the pressure-induced magnetic phase in FeSe by analyzing how pressure affects Coulomb interactions, leading to reduced nematic order and the emergence of magnetic stripe order, aligning with experimental phase diagrams.

Contribution

It provides a self-consistent theoretical framework linking pressure-induced Coulomb interaction changes to magnetic and nematic phase evolution in FeSe.

Findings

Pressure decreases nearest-neighbor Coulomb repulsion.

Reduction in nematic order under pressure.

Emergence of magnetic stripe order at high pressure.

Abstract

We offer an explanation for the recently observed pressure-induced magnetic state in the iron-chalcogenide FeSe based on \textit{ab initio} estimates for the pressure evolution of the most important Coulomb interaction parameters. We find that an increase of pressure leads to an overall decrease mostly in the nearest-neighbor Coulomb repulsion, which in turn leads to a reduction of the nematic order and the generation of magnetic stripe order. We treat the concomitant effects of band renormalization and the induced interplay of nematic and magnetic order in a self-consistent way and determine the generic topology of the temperature-pressure phase diagram, and find qualitative agreement with the experimentally determined phase diagram.