Phase diagrams of half-filled 1D and 2D extended Hubbard model within COM

TL;DR

This study uses the 2-pole approximation within the Composite Operator Method to analyze phase diagrams of the half-filled extended Hubbard model in 1D and 2D, aiming to better describe features of organic superconductors and cuprates.

Contribution

It introduces an improved theoretical approach to analyze phase transitions in the extended Hubbard model, capturing complex features like reentrant behavior.

Findings

Phase diagrams show paramagnetic metal-insulator transitions.

Identification of charge-ordered phases and critical points.

Reentrant phase transition behavior observed.

Abstract

The half-filled extended Hubbard model, in one and two dimensions, is studied by means of the 2-pole approximation within the Composite Operator Method with the aim at improving the possibilities to describe some of the experimental features observed for quasi-1D organic superconductors and Cu-O planes of cuprates. The phase diagrams ($T$-$V$ and $V$-$U$) are analyzed with respect to the paramagnetic metal - paramagnetic insulator - charge ordered phase transitions. The relevant features of the diagrams (rank of the phase transitions, critical points, reentrant behavior) are discussed in detail.