Mesoscopic Phase Separation in the Model with Competing Jahn-Teller and Coulomb Interaction

TL;DR

This paper investigates how competing Jahn-Teller and Coulomb interactions influence phase separation in a model, revealing different segregation patterns at varying densities through theoretical derivation and Monte Carlo simulations.

Contribution

It derives the interaction between Jahn-Teller centers and formulates an effective model to describe phase separation phenomena at different densities.

Findings

Phase separation occurs at low temperatures without Coulomb repulsion.

Coulomb repulsion leads to short-scale phase separation.

Charged bubbles form at low density, domain walls at high density.

Abstract

We have derived the interaction between Jahn-Teller centers due to optical and acoustic phonons. Without Coulomb repulsion the model leads to a global phase separation at low temperature. At long distances Coulomb repulsion always dominates the short range attraction leading to phase separation on a short scale. On the basis of Monte-Carlo simulation of microscopic lattice-gas model we have formulated an effective phenomenological model. In the limit of low density of polarons, phase separation takes place in the form of charged bubbles. In the limit of high density, charge segregation occurs on domain walls.