4-pole analysis of the two-dimensional Hubbard model

TL;DR

This paper investigates the electronic states of the 2D Hubbard model using a 4-pole approximation, revealing complex features like quasi-particle peaks, shadow bands, and band flatness related to spin and charge configurations.

Contribution

It introduces a novel 4-pole approximation within the Composite Operator Method that incorporates operators capturing spin and charge environment effects.

Findings

Identification of a quasi-particle peak at the Fermi level

Observation of shadow bands and band flatness at (pi, 0)

Analysis of energy scale J=4t^2/U effects

Abstract

The electronic states of the two-dimensional Hubbard model are investigated by means of a 4-pole approximation within the Composite Operator Method. In addition to the conventional Hubbard operators, we consider other two operators, which come from the hierarchy of the equations of motion. These operators carry information regarding surrounding spin and charge configurations. By means of this operatorial basis, we can study the physics related to the energy scale J=4t^2/U. Results present, in addition to the main two bands, a quasi-particle peak at the Fermi level, shadow bands and band flatness at (pi, 0) point.