Universal Aspects of Coulomb Frustrated Phase Separation

TL;DR

This paper explores how Coulomb interactions influence phase transitions in electronic systems, revealing universal instability to intermediate microemulsion phases in 2D and conditions preventing phase separation in 3D, with implications for various dimensionalities.

Contribution

It demonstrates the universal instability to microemulsion phases in 2D and conditions for phase separation suppression in 3D due to Coulomb interactions.

Findings

In 2D, systems near critical density form microemulsion phases.

In 3D, strong Coulomb interactions prevent phase separation.

Anisotropic systems exhibit a staircase of phase transitions.

Abstract

We study the consequences of Coulomb interactions on a system undergoing a putative first order phase transition. In two dimensions (2D), near the critical density, the system is universally unstable to the formation of new intermediate phases, which we call ``electronic microemulsion phases,'' which consist of an intermediate scale mixture of regions of the two competing phases. A correlary is that there can be no direct transition as a function of density from a 2D Wigner crystal to a uniform electron liquid. In 3D, %we find that if the strength of the Coulomb interactions exceeds a critical value, no phase separation occurs, while for weaker Coulomb strength, electronic microemulsions are inevitable. This tendency is considerably more pronounced in anisotropic (quasi 2D or quasi 1D) systems, where a devil's staircase of transitions is possible.