Electronic States and Metal-Semiconductor Transition in BaPb_1−xBi_xO₃

抄録

The electronic structure of BaPb_1−xBi_xO₃ (BPB) is calculated in the framework of mean field approximation and coherent potential approximation, describing the electronic motion in terms of the extended Hubbard model with two kinds of site-dependent parameters; difference in the on-site energies on Bi and Pb sites and effective on-site interaction due to the oxygen breathing modes. Three characteristic band-shapes are obtained as a function of Bi concentration x; a single band and pseudo-gapped band for metallic phase and two separated bands for semiconducting phase, indicating that x plays a role similar to that of the temperature in the case of the Peierls instability. These results are successfully applied to interpret the main features of metal-semiconductor transition of BPB obtained from optical spectra.