Monte Carlo study of phase separation in magnetic insulators

TL;DR

This study uses Monte Carlo simulations to explore phase separation and magnetic ordering in a two-dimensional extended Hubbard model with intersite magnetic interactions, revealing phase transitions and tricritical points.

Contribution

It provides new insights into phase separation and magnetic phases in the extended Hubbard model using Monte Carlo methods on a 2D lattice.

Findings

Identification of phase separation between AF and NO phases.

Observation of first and second order AF-NO transitions.

Presence of a tricritical point in the phase diagram.

Abstract

In this work we focus on the study of phase separation in the zero-bandwidth extended Hubbard with nearest-neighbors intersite Ising-like magnetic interactions $J$ and on-site Coulomb interactions $U$. The system has been analyzed by means of Monte Carlo simulations (in the grand canonical ensemble) on two dimensional square lattice (with $N=L\times L =400$ sites) and the results for $U/(4J)=2$ as a function of chemical potential and electron concentration have been obtained. Depending on the values of interaction parameters the system exhibits homogeneous (anti-)ferromagnetic (AF) or non-ordered (NO) phase as well as phase separation PS:AF/NO state. Transitions between homogeneous phases (i.e. AF-NO transitions) can be of first or second order and the tricritical point is also present on the phase diagrams. The electron compressibility $K$ is an indicator of the phase separation and that quantity is of particular interest of this paper.