T_c and pseudogap in the 2-D attractive Hubbard model

Abstract

In the fully self-consistent T-matrix formulation, which includes pair fluctuations for T ≥ Tc in a natural way, we have evaluated the critical temperature Tc by studying the divergence of the real part of the T-matrix at ω = 0 and q = 0 (Thouless criterion). Moreover, we found strong evidence for the appearance of a pseudogap in the density of states, N(ω), around the chemical potential, μ, with reduced temperature. Our calculations are carried out for the case in which correlations are important, i.e. U/t = -4.0. The pseudogap is consistent with numerical and analytical calculations and shows that correlations for T ≥ Tc have important consequences on the density of states. © 1995.