Spectral properties of the attractive Hubbard model

Abstract

Deviations from Fermi liquid behavior are well documented in the normal state of the cuprate superconductors, and some of these differences are possibly related to pre-formed pairs appearing at temperatures above Tc. In order to test these ideas we have investigated the attractive Hubbard model within a self-consistent, conserving ladder approximation. In this version of the theory, no feature is present which can be related to the pseudo gap found in the high-Tc materials. Further, the interactions between two-particle bound states change the physics of the superconducting instability in a profound fashion, and lead to a completely different phenomenology that one predicts based on the non-self-consistent version of the same theory.

Pairing fluctuations and pseudogaps in the attractive Hubbard model

“…At low density, [73][74][75] or with additional approximations, 76 a pseudogap may be found. By contrast, when the q ជ ϭ0 superconducting mode is relaxational, selfconsistent T-matrix calculations 77 have failed to show a pseudogap in the one-particle spectral function A(k F ,) ϭϪ2ImG R (k F ,) when the momentum dependence of the self-energy is neglected ͑which should be valid in infinite dimension͒. In two dimensions, an absence of the pseudogap would be in sharp contrast with various QMC results 39,49 and with general physical arguments inspired by studies of the repulsive case, 53,78 which have already stressed that space dimension is crucial in the physics of pseudogap formation.…”