Pseudogap in the one-electron spectral functions of the attractive Hubbard model

TL;DR

This paper investigates the pseudogap phenomenon in the 2D attractive Hubbard model by coupling electrons to pair fluctuations, revealing a pseudogap at high temperatures and a superconducting gap below the transition temperature.

Contribution

It introduces a method to calculate the one-electron Green's function considering pair fluctuations modeled by XY-model correlations.

Findings

Pseudogap appears at temperatures above $T_C$

Superconducting gap emerges below $T_C$ in quasi-3D systems

Electronic density of states shows pseudogap behavior

Abstract

We calculate the one-electron Green's function of the 2D attractive Hubbard model by coupling the electrons to pair fluctuations. The latter are approximated by homogeneous amplitude fluctuations and phase correlations corresponding to the XY-model. The electronic density of states shows a pseudogap at temperatures well above the transition temperature $T_{C}$. For a quasi-3D system, a superconducting gap emerges out of the pseudogap below $T_{C}$.