Self-organization of charged particles on a 2D lattice subject to anisotropic Jahn-Teller-type interaction and 3D Coulomb repulsion

TL;DR

This paper investigates how charged particles self-organize into mesoscopic structures on a 2D lattice under competing interactions, revealing phase transitions, cluster formations, and potential links to phenomena like superconductivity in oxides.

Contribution

It introduces a comprehensive Monte Carlo simulation study of charged particle self-organization considering anisotropic Jahn-Teller and Coulomb interactions, highlighting new phase behaviors and cluster stability.

Findings

Mesoscopic phase separation occurs due to competition between ordering and Coulomb energies.

Charged clusters with even numbers of particles are more stable over a wide density range.

Multiple crossovers between different cluster sizes are observed as temperature and density vary.

Abstract

Self-organization of charged particles on a 2D lattice, subject to an anisotropic Jahn-Teller-type interaction and 3D Coulomb repulsion is investigated. In the mean-field approximation without Coulomb interaction, the system displays a phase transition of first order. In the presence of the Coulomb repulsion the global phase separation becomes unfavorable and the system shows a mesoscopic phase separation, where the size of the charged regions is determined by the competition between the ordering energy and the Coulomb energy. The phase diagram of the system as a function of particle density and temperature is obtained by systematic Monte Carlo simulations. With decreasing temperature a crossover from a disordered state to a state composed from mesoscopic charged clusters is observed. In the phase separated state charged clusters with even number of particles are more stable than those with odd number of particles in a large range of particle densities. With increasing particle density at low temperatures a series of crossovers between states with different cluster sizes is observed. Above half filling in addition to the low temperature clustering another higher temperature scale, which corresponds to orbital ordering of particles, appears. We suggest that the diverse functional behaviour - including superconductivity - observed in transition metal oxides can be thought to arise from the self-organization of this type.