Superconductivity inBa1−xKxBiO3

Abstract

Superconductivity in ${\mathrm{Ba}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{K}}_{\mathit{x}}$${\mathrm{BiO}}_{3}$ is studied within the framework of Eliashberg theory using a model of the electron-phonon interaction, ${\mathrm{\ensuremath{\alpha}}}^{2}$F(\ensuremath{\omega}). The model is based upon molecular-dynamics calculations of the phonon density of states, which are in good agreement with inelastic-neutron-scattering experiments. The function \ensuremath{\alpha}(\ensuremath{\omega}) is constructed using information from electron-tunneling experiments. Our model is constructed with the premise that the electron-phonon coupling constant \ensuremath{\lambda}\ensuremath{\approxeq}1 and that strong electron-phonon coupling exists for high-energy (30--60 meV) phonon modes. Superconducting properties of the material at zero and finite temperatures are calculated and compared with experiments.