Why MgFeGe is not a superconductor

TL;DR

This paper investigates why MgFeGe, despite structural similarities to superconducting LiFeAs, does not exhibit superconductivity, highlighting the importance of magnetic properties and spin fluctuations in Fe-based superconductors.

Contribution

The study reveals that magnetic differences in MgFeGe explain its lack of superconductivity, supporting theories that link spin fluctuations to superconductivity in Fe-based materials.

Findings

MgFeGe differs magnetically from LiFeAs in the magnetic domain.

The absence of superconductivity in MgFeGe supports spin fluctuation theories.

Electronic structures are similar without spin polarization, but magnetic states differ.

Abstract

The recently synthesized MgFeGe compound is isostructural and isoelectronic with superconducting LiFeAs. Both materials are paramagnetic metals at room temperature. Inspection of their electronic structures without spin polarization reveals hardly any difference between the two. This fact was interpreted as evidence against popular theories relating superconductivity in Fe-based materials with spin fluctuations. We show that in the magnetic domain the two compounds are dramatically different, and the fact that MgFeGe does not superconduct, is, on the contrary, a strong argument in favor of theories based on spin fluctuations.