The role of electron-phonon interaction in oxide superconductors

The electron-phonon (EP) interaction and lattice dynamics are investigated microscopically for oxide superconductors, Ba_xK_1-xBiO₃ (BKB) and La_2-xSr_xCuO₄ (LSC), on the basis of their realistic tight-bi nding bands fitted to the first-principle bands of each compound. By using the EP interaction and renormalized phonons we have calculated the spectral functions of BKB and LSC. In the framework of the phonon-mediated pairing mechanism, superconducting properties such as the transition temperature, the gap function and the tunneling spectra are calculated by solving the Eliashberg equation. The results for BKB are in good agreement with observations. For LSC, the calculated results are compared with recent observations and discussed in connection with those for BKB.