GW study of the half-metallic Heusler compounds Co2MnSi and Co2FeSi

TL;DR

This study uses the GW approximation to accurately compute quasiparticle spectra of Co2MnSi and Co2FeSi Heusler compounds, revealing significant many-body effects especially in Co2FeSi, and showing good agreement with experimental spectra.

Contribution

It demonstrates the importance of many-body corrections in Co2FeSi and validates the Kohn-Sham eigenvalues as a reasonable approximation for quasiparticle spectra in these compounds.

Findings

Many-body corrections are crucial for Co2FeSi, opening a pseudogap.

Calculated spectra agree well with experimental photoemission and x-ray absorption data.

Kohn-Sham eigenvalues approximate quasiparticle spectra reasonably well.

Abstract

Quasiparticle spectra of potentially half-metallic Co2MnSi and Co2FeSi Heusler compounds have been calculated within the one-shot GW approximation in an all-electron framework without adjustable parameters. For Co2FeSi the many-body corrections are crucial: a pseudogap opens and good agreement of the magnetic moment with experiment is obtained. Otherwise, however, the changes with respect to the density-functional-theory starting point are moderate. For both cases we find that photoemission and x-ray absorption spectra are well described by the calculations. By comparison with the GW density of states, we conclude that the Kohn-Sham eigenvalue spectrum provides a reasonable approximation for the quasiparticle spectrum of the Heusler compounds considered in this work.