Phase transition in the ''superconducting glass'' model

We study the superconducting transition in a system described by the Hubbard Hamiltonian with negative U-centers (attraction between electrons with opposite spins on one site). We derive and solve in the self-consistent field approximation equations for the modulus of the order parameter and the chemical potential. We show that the superconducting transition is the result of Bose condensation of electron pairs. The formula for the transition temperature is T/sub c/ = W(1--2ν)/ln(ν-1--1), where W is the band width and 2ν is the number of electrons per site. We calculate the thermodynamic quantities and the current. We write down equations for a disordered model (''superconducting glass''). In the simplest case of two ideal sublattices their solution gives a steep decrease in T/sub c/ when the single-site energy spread increases