DENSITY OF STATES, NUCLEAR-RELAXATION RATE, AND THERMAL-CONDUCTIVITY IN HIGH-TC SUPERCONDUCTORS

We solve the Eliashberg equations for the self-energy of quasiparticles in a two-dimensional band, interacting via exchange of phonons and antiparamagnons. The interaction due to exchange of spin and charge fluctuations is calculated self-consistently within the random-phase approximation for the Hubbard model. The pair breaking caused by spin fluctuations leads to a gapless density of states near T(c), to a rapid drop of the nuclear-spin-lattice relaxation rate below T(c), and to a gradual upturn of the phonon thermal conductivity below T(c). In the superconducting state there occurs a pseudogap in the dynamical structure factor for neutron scattering. Our results are in qualitative agreement with the experimental data on YBa2Cu3O7.