# Phase diagrams of a 2D Ising spin-pseudospin model

## TL;DR

This paper investigates the phase behavior of a 2D spin-pseudospin model relevant to high-Tc cuprates, revealing how magnetic and charge orderings compete and lead to phase separation, supported by mean-field and Monte Carlo analyses.

## Contribution

It provides the first mean-field and Monte Carlo comparison of the 2D spin-pseudospin model, highlighting the conditions for phase separation and deriving an analytical PS temperature expression.

## Key findings

- Strong exchange leads to phase separation into charge and spin subsystems.
- Mean-field results qualitatively agree with Monte Carlo simulations.
- Analytical expression for the phase separation temperature was derived.

## Abstract

We consider the competition of magnetic and charge ordering in high-Tc cuprates within the framework of the simplified static 2D spin-pseudospin model. This model is equivalent to the 2D dilute antiferromagnetic (AFM) Ising model with charged impurities. We present the mean-field results for the system under study and make a brief comparison with classical Monte Carlo (MC) calculations. Numerical simulations show that the cases of strong exchange and strong charge correlation differ qualitatively. For a strong exchange, the AFM phase is unstable with respect to the phase separation (PS) into the charge and spin subsystems, which behave like immiscible quantum liquids. An analytical expression was obtained for the PS temperature.