Hexatic and mesoscopic phases in the 2D quantum Coulomb system

TL;DR

This study investigates the melting behavior of a 2D quantum Coulomb system using quantum Monte Carlo, revealing unique quantum effects, deviations from classical theories, and the absence of stable mesoscopic phases.

Contribution

It provides the first detailed phase diagram of the 2D quantum Coulomb system and analyzes quantum effects on melting and hexatic phases.

Findings

Quantum effects significantly alter melting behavior.

The hexatic phase decay exponent differs from Kosterlitz-Thouless predictions.

No stable mesoscopic phase found in equilibrium.

Abstract

We study the Wigner crystal melting in a two dimensional quantum system of particles interacting via the 1/r Coulomb potential. We use quantum Monte Carlo methods to calculate its phase diagram, locate the Wigner crystal region, and analyze its instabilities towards the liquid phase. We discuss the role of quantum effects in the critical behavior of the system, and compare our numerical results with the classical theory of melting, and the microemulsion theory of frustrated Coulomb systems. We find a Pomeranchuk effect much larger then in solid helium. In addition, we find that the exponent for the algebraic decay of the hexatic phase differs significantly from the Kosterilitz-Thouless theory of melting. We search for the existence of mesoscopic phases and find evidence of metastable bubbles but no mesoscopic phase that is stable in equilibrium.