Superconductivity and metal-semiconductor transition in BaPb1-xBixO3

Abstract

The perovskite solid solutions BaPb_1-xBi_xO₃ exhibit unique properties in both metallic and semiconducting phases. In the metallic phase (0 ≤ x ≤ 0.35) they are superconducting with high transition temperatures. It turns out that the high T _c originates from extremely strong electron-phonon interaction. At the metal-semiconductor transition the superconductivity disappears and the semiconducting properties persist over a wide range of Bi composition (0.35 ≤ x ≤ 1). Recent studies of the optical spectrum, as well as Raman scattering experiments, have given direct evidence for charge-density-wave formation in BaBiO₃. The CDW is found to be local in the present system and be stable throughout the semiconducting phase. The local CDW instability appears to manifest itself even in the metallic phase, giving rise to various precursory effects.