PUB - Publikationen an der Universität Bielefeld

A self-consistent microscopic theory for the 2D Hubbard Hamiltonian and additional electron-phonon interaction yields below T(c) a gap in the quasiparticle decay rate as well as in the spin and charge fluctuation spectra. The mass enhancement and the quasiparticle decay rate exhibit in the normal state "marginal" Fermi liquid behavior while in the superconducting state the quasiparticle character is restored. These properties lead to anomalous behavior of the dynamic conductivity: considered as a function of temperature a peak evolves at T(c) as the frequency is decreased well below 2-DELTA. In the optical conductivity, considered as a function of frequency, a gap between 2-DELTA and 4-DELTA opens rapidly as T is decreased below, T(c). Our results are in qualitative agreement with experiments on high-T(c) superconductors.