Experimental and theoretical study of the electronic structure of single-crystal BaBiO3

High quality single crystals of BaBiO3 were grown by congruent melting technique and characterized with x-ray diffraction, x-ray photoemission, and transport property studies. The perovskite oxide BaBiO3 is a negative charge transfer gap high T-c oxide parent superconducting compound exhibiting self-doping of holes into the oxygen 2p band. We study the low energy scale valence and conduction bands in detail from both a theoretical perspective as well as through x ray, absorption/emission, and photoelectron spectroscopies. X-ray spectroscopy verifies the results of density functional theory (DFT) regarding the overall band structure featuring strong O 2p character of the empty antibonding combination of the hybridized Bi 6s and O 2p states. From the analysis of the core level line shapes we conclude that the dominant O 2p-Bi 6s hybridization energy scale determines the low energy scale electronic structure. This analysis provides further insight into the importance of self-doped oxygen 2p states in this high Tc family of oxides.