Effect of 3d-doping on the electronic structure of BaFe2As2

TL;DR

This study investigates how doping BaFe2As2 with Co, Ni, and Cu affects its electronic structure, revealing that Co and Ni introduce free carriers near the Fermi level, unlike localized Cu states, which explains differences in superconductivity.

Contribution

The paper provides experimental evidence detailing the distribution of 3d states of Co, Ni, and Cu in BaFe2As2, clarifying their roles in electronic structure and superconductivity.

Findings

Co and Ni 3d states add free carriers at the Fermi level.

Cu 3d states are localized at the bottom of the valence band.

Superconductivity occurs with Co and Ni doping, not Cu.

Abstract

The electronic structure of BaFe2As2 doped with Co, Ni, and Cu has been studied by a variety of experimental and theoretical methods, but a clear picture of the dopant 3d states has not yet emerged. Herein we provide experimental evidence of the distribution of Co, Ni, and Cu 3d states in the valence band. We conclude that the Co and Ni 3d states provide additional free carriers to the Fermi level, while the Cu 3d states are found at the bottom of the valence band in a localized 3d10 shell. These findings help shed light on why superconductivity can occur in BaFe2As2 doped with Co and Ni but not Cu.