EFFECTS OF HOLE DOPING AND ELECTRON-PHONON INTERACTION ON THE ELECTRONIC-STRUCTURE OF BA1-XKXBIO3 STUDIED BY PHOTOEMISSION SPECTROSCOPY

The electronic structure of Ba1-xKxBiO3 has been studied by photoemiss ion spectroscopy. With increasing x, the spectra are generally shifted towards the Fermi level (E(F)), indicating a downward shift of E(F) d ue to hole doping. The magnitudes of the shifts, however, are substant ially smaller than those predicted by band-structure calculations. In the cubic metallic phase, although band-structure calculations on the cubic structure predict the density of states (DOS) to show a peak at or close to E(F), the photoemission intensity decreases towards E(F), suggesting that the splitting of the Bi 6s band persists and results i n a pseudogap behavior. We propose that the suppression of the DOS pea k at E(F) is caused by dynamical lattice distortion: The DOS peak pred icted for the cubic structure presumably induces the lattice instabili ty, leading to the dynamical lattice distortion.