New solutions of the T-matrix theory of the attractive Hubbard model

Abstract

We present a novel solution method with which we obtain the spectral functions of the attractive Hubbard model in two dimensions in a non self-consistent formulation of the T-matrix approximation. We use a partial fraction decomposition of the self energy from which we obtain the single-particle spectral functions to a remarkably high accuracy. Here we find the poles and residues of the self energy to a relative accuracy of 10 −80 for an 8 × 8 lattice, and plot the resulting density of states. Our results show pseudogap physics as T c is approached from above; these analytical results are in agreement with recent Quantum Monte Carlo data.