Competing phases in kagome magnet FeGe from functional renormalization

TL;DR

This study investigates the competing electronic phases in the kagome magnet FeGe using combined DFT and functional renormalization group methods, revealing a complex interplay of charge density waves, pairing, and spin instabilities that could lead to superconductivity.

Contribution

It introduces a detailed phase diagram for FeGe based on interaction parameters and highlights the competition among various electronic orders in a magnetic kagome metal.

Findings

FeGe exhibits strong competition between charge density wave, pairing, and spin Pomeranchuk instabilities.

The electronic correlations are primarily 2D and originate from Van Hove points at M points.

Slightly increasing nearest-neighbor interactions may induce superconductivity in FeGe.

Abstract

The discovery of a charge density wave in FeGe extends the discussion of the nature of charge order in kagome metals to a magnetic compound. Motivated by this observation, we combine density functional theory (DFT) and functional-renormalization-group calculations to study interaction-induced Fermi-surface instabilities of the magnetic state of FeGe. We argue that the leading intra-band contribution to electronic correlations are approximately 2D and come from Van Hove points at the projected $M$~points. By varying parameters around DFT values, we determine a phase diagram for the quasi-2D scenario as function of on-site and nearest-neighbor interactions. We discuss universal aspects in the electronic mechanisms for the resulting phases, as well as the role of SU(2) symmetry breaking. We find FeGe to be in a regime of strong competition between $p$-wave charge density wave, $f$-wave pairing, and $d$-wave spin Pomeranchuk instabilities. This interplay can be influenced in favor of superconducting pairing for slightly increased nearest-neighbor interaction, suggesting a potential to induce superconductivity in FeGe.