Spectral photoconductivity of the BaPb1-xBixO3system with a proposal for the electronic structure

Abstract

Abstract A series of systematic studies of transient photoconductivity has been made on the BaPb1-x Bi x O3 system in the semiconductive phase. On the basis of the new experimental results, we propose a new model for the electronic structure and the optical transitions for the BaPb1-x Bi x O3 system in the semiconductive phase in a consistent way together with the previous data. The semiconductive nature of BaBiO3 is attributed to its electronic structure, essentially similar to that of Bi2O3 with localization of an excess hole on the O2- ion per formula unit of BaBiO3. This model is different from one based on the splitting of the Bi–6s state due to local charge-density-wave formation. If we extend the proposed electronic structure to cover that of the superconductive phase, we obtain a resultant electronic structure similar to those of the Cu-based superconductors, at least near the Fermi level. Thus, we recognize that this feature may reveal a common mechanism for both Cu-based and BiO-based high-Tc oxide superconductors.