Charge orderings in the atomic limit of the extended Hubbard model

TL;DR

This paper investigates charge orderings in the atomic limit of the extended Hubbard model on a square lattice using Monte Carlo simulations, revealing complex phase diagrams with multiple phases and multicritical points.

Contribution

It provides a detailed phase diagram of the AL-EHM, identifying three charge ordered phases and analyzing multicritical behavior, comparing it with the Blume-Capel model.

Findings

Identification of three charge ordered phases

Rich multicritical behavior observed

Comparison with the Blume-Capel model

Abstract

The extended Hubbard model in the atomic limit (AL-EHM) on a square lattice with periodic boundary conditions is studied with use of the Monte Carlo (MC) method. Within the grand canonical ensemble the phase and order-order boundaries for charge orderings are obtained. The phase diagrams include three types of charge ordered phases and the nonordered phase. The system exhibits very rich structure and shows unusual multicritical behavior. In the limiting case of tij = 0, the EHM is equivalent to the pseudospin model with single-ion anisotropy 1/2U, exchange interaction W in an effective magnetic field (mu-1/2U-zW). This classical spin model is analyzed using the MC method for the canonical ensemble. The phase diagram is compared with the known results for the Blume-Capel model.