Influence of long-range and strong correlation effects on the electron-phonon coupling in high-T _c oxides

Abstract

Calculations of the Eliashberg functionα ²F and the corresponding transport functionα ² _tr F for high-T _c oxides are presented using a screened ionic model (rigidly shifted ionic potentials screened by charge carriers in the CuO₂ planes within the RPA) for the electron-phonon coupling. It is shown that this model yields a large difference between the transport and the superconducting electron-phonon interaction due to imperfect screening and contributions beyond nearest-neighbor interactions. Using these results, the electron and the lattice heat conductivities are calculated both in the normal and the superconducting state and compared with experiment. Finally, effects due to a strong on-site electron-electron repulsion are included in leading order in an 1/N expansion, whereN is the number of spin degrees of freedom. In particular, it is shown for the infiniteU, one-band Hubbard model that correlations tend to suppressα ² _tr F strongly andα ² F somewhat.