Role of the attractive intersite interaction in the extended Hubbard model

TL;DR

This paper exactly solves the extended Hubbard model on a Bethe lattice with attractive intersite interaction, revealing phase separation, reentrant behavior, and thermodynamic properties near criticality.

Contribution

It provides an exact solution for the extended Hubbard model with attractive intersite interaction, analyzing phase transitions and thermodynamics.

Findings

Phase separation occurs at finite temperature.

Reentrant behavior observed in phase diagram.

Critical temperature depends on U/|V|, n, and z.

Abstract

We consider the extended Hubbard model in the atomic limit on a Bethe lattice with coordination number z. By using the equations of motion formalism, the model is exactly solved for both attractive and repulsive intersite potential V. By focusing on the case of negative V, i.e., attractive intersite interaction, we study the phase diagram at finite temperature and find, for various values of the filling and of the on-site coupling U, a phase transition towards a state with phase separation. We determine the critical temperature as a function of the relevant parameters, U/|V|, n and z and we find a reentrant behavior in the plane (U/|V|,T). Finally, several thermodynamic properties are investigated near criticality.