Electronic band structure of BaCo₂As₂: A fully doped ferropnictide analog with reduced electronic correlations

We report an investigation with angle-resolved photoemission spectroscopy of the Fermi surface and electronic band structure of BaCo₂As₂. Although its quasinesting-free Fermi surface differs drastically from that of its Fe-pnictide cousins, we show that the BaCo₂As₂ system can be used as an approximation to the bare unoccupied band structure of the related BaFe_2-xCo_xAs₂ and Ba_1-xK_xFe₂As₂ compounds. However, our experimental results, in agreement with dynamical-mean-field-theory calculations, indicate that electronic correlations are much less important in BaCo₂As₂ than in the ferropnictides. Our findings suggest that this effect is due to the increased filling of the electronic 3d shell in the presence of significant Hund's exchange coupling.