ELECTRON-PHONON INTERACTION AND SUPERCONDUCTIVITY IN OXIDE SUPERCONDUCTORS La2−xSrxCuO4

Abstract

Effects of electron-phonon interaction on lattice dynamics in oxide superconductors La 2−x Sr x CuO 4 (LSC) are studied microscopically on the basis of the tight-binding band fitted to the first principle band. Breathing-type vibrations of oxygen atoms in the CuO 2 plane are renormalized significantly at around (π/a, π/a, 0) and (π/a, 0, 0) due to strong dependences of the electron-phonon interaction on wavevectors and phonon modes. In the framework of the usual phonon-mediated pairing mechanism, superconducting properties, such as transition temperatures and tunneling spectra, are studied by solving isotropic Eliashberg equations. The spectral function α2F(ω) has a characteristic structure over a wide energy range below 85 meV. The tunneling conductance d I/ d V and its derivative d 2I/ d V2 calculated have prominent peaks below 40 meV, which show good correspondences to those observed by recent tunneling experiments.