Anisotropic strong coupling calculation of the local electromagnetic response of high-T-c superconductors

The electromagnetic response of the CuO2-planes is calculated within a stro ng coupling theory using model Light binding bands and momentum dependent p airing interactions representing spin fluctuation and phonon exchange. The superconducting state resulting from these interactions has d-wave symmetry . With phonon exchange included the order parameter amplitude grows rapidly below T-c at elevated frequencies which leads to improved agreement with t he observed temperature dependence of the penetration depth. Good agreement between theory and experiment can only be achieved if it is assumed that t he strength of the quasiparticle interaction decreases with temperature in the superconducting state. The amount of this reduction depends sensitively on the momentum dependence of the interactions, the energy dispersion and the position of the Fermi line. (C) 1998 Elsevier Science Ltd. All rights r eserved.