THEORY OF OPTICAL CONDUCTIVITY AND PHOTOEMISSION INTENSITY FOR CU-O PLANE SUPERCONDUCTORS

The quasiparticle self-energy and the dynamic spin and charge susceptibilities are calculated self-consistently in RPA for the two-dimensional Hubbard model with additional electron-phonon interaction. Vertex corrections lead to an enhancement of charge fluctuations and a suppression of spin fluctuations, thus increasing T(c). The resulting optical reflectivity in the normal and superconducting state is found to be in qualitative agreement with the experimental data on YBa2Cu3O7 for intermediate values of lambda(ph) and U/t. We calculate also the photoemission intensity in the normal and superconducting state.