Evidence for a Pseudogap Above the Critical Temperature in the Attractive Hubbard Model

1994/05/25 by Rodríguez-Núñez, J. J., Schafroth, S., Micnas, R. +3
#Condensed Matter (cond-mat) #FOS: Physical sciences

paper · doi:10.48550/arxiv.cond-mat/9405071

Abstract

We explore the effect of fluctuations for T ≥ T_c in the 2-D negative Hubbard model within the framework of the selfconsistent T-matrix formalism, which goes beyond the BCS approximation and includes pair fluctuations. We enter the regime where correlations are important, namely, U/t = -4.0, where t denotes the hopping matrix element between nearest neighboors and U is the strength of the on-site interaction. Our results include: 1) In comparison to the free case, the distribution function, n(\bf k), reveals considerable renormalization. This fact makes us conclude that the Fermi surface is blurred for correlated electron systems; 2) There is a pseudogap in the density of states, N(ω), around the chemical potential, μ; and 3) The real part of the T-matrix, at zero frequency and zero momentum, vs T/t shows a divergence at a particular temperature. This last result shows that more approximate T-matrix calculations, extended to T~=~0 are meaningless.

Related

• The Attractive Hubbard Model in 2D: Is it capable of describing a pseudogap and preformed pairs?
• Remnant Fermi surface in a pseudogap regime of the two-dimensional Hubbard model at finite temperature
• Anisotropic pseudogap in the half-filling 2-d Hubbard model at finite T
• Location and thermal evolution of the pseudogap due to spin fluctuations
• Pair fluctuation effects above T_{\rm c}