One-Electron Spectral Functions of the Attractive Hubbard Model for Intermediate Coupling

TL;DR

This paper analyzes the one-electron spectral function of the attractive Hubbard model at intermediate coupling and low density, providing an approximate analytical self-energy and revealing a three-branch excitation spectrum.

Contribution

It introduces an analytical approach using the self-consistent T-matrix approximation for the attractive Hubbard model in a specific regime.

Findings

Spectral function exhibits three excitation branches.

Self-energy derived in an approximate analytical form.

Method compatible with the Mermin-Wagner theorem.

Abstract

We calculate the one-electron spectral function of the attractive (negative-$U$) Hubbard model. We work in the intermediate coupling and low density regime and obtain the self-energy in an approximate analytical form. The excitation spectrum is found to consist of three branches. The results are obtained in a framework, based on the self-consistent T-matrix approximation, which is compatible with the Mermin-Wagner theorem.