Phase separation and second-order phase transition in the phenomenological model for Coulomb frustrated 2D system

TL;DR

This paper models phase separation and second-order phase transitions in a Coulomb frustrated 2D system, revealing various phase-separated states and their transitions as temperature decreases.

Contribution

It introduces a phenomenological model considering charge coupling as local temperature, demonstrating phase separation and complex state formations in 2D Coulomb systems.

Findings

Identification of phase-separated states ('stripes', 'rings', 'snakes')

Parameter ranges for different states

Sequence of phase transitions with temperature decrease

Abstract

We have considered the model of the phase transition of the second order for the Coulomb frustrated 2D charged system. The coupling of the order parameter with the charge was considered as the local temperature. We have found that in such system, an appearance of the phase-separated state is possible. By numerical simulation, we have obtained different types ("stripes", "rings", "snakes") of phase-separated states and determined the parameter ranges for these states. Thus the system undergoes a series of phase transitions when the temperature decreases. First, the system moves from the homogeneous state with a zero order parameter to the phase-separated state with two phases in one of which the order parameter is zero and, in the other, it is nonzero ($\tau>0$). Then a first-order transition occurs to another phase-separated state, in which both phases have different and nonzero values of the order parameter (for $\tau<0$). And only a further decrease of temperature leads to a transition to a homogeneous ordered state.