Electronic band structure of BaCo$_{2}$As$_2$: a fully-doped ferropnictide with reduced electronic correlations

TL;DR

This study uses photoemission spectroscopy to analyze BaCo₂As₂'s electronic structure, revealing reduced electronic correlations compared to related ferropnictides, due to increased 3d shell filling and Hund's coupling.

Contribution

It provides the first detailed experimental and theoretical analysis of BaCo₂As₂'s band structure, highlighting its reduced correlations and differences from Fe-based ferropnictides.

Findings

BaCo₂As₂ has a drastically different Fermi surface from Fe-pnictides.

Electronic correlations are significantly weaker in BaCo₂As₂.

The reduced correlations are linked to increased 3d shell filling and Hund's exchange.

Abstract

We report an angle-resolved photoemission spectroscopy investigation of the Fermi surface and electronic band structure of BaCo$_{2}$As$_2$. Although its quasi-nesting-free Fermi surface differs drastically from that of its Fe-pnictide cousins, we show that the BaCo$_{2}$As$_2$ system can be used as an approximation to the bare unoccupied band structure of the related BaFe$_{2-x}$Co$_x$As$_2$ and Ba$_{1-x}$K$_x$Fe$_2$As$_2$ compounds. However, our experimental results, in agreement with dynamical mean field theory calculations, indicate that electronic correlations are much less important in BaCo$_{2}$As$_2$ than in the ferropnictides. Our findings suggest that this effect is due to the increased filling of the electronic 3$d$ shell in the presence of significant Hund's exchange coupling.