Melting Scenario for Coulomb-interacting Classical Particles in Two-dimensional Irregular Confinements

TL;DR

This study uses Monte Carlo simulations to explore how Coulomb-interacting particles in irregular 2D confinements transition from solid-like to liquid-like phases, revealing defect-mediated melting driven by thermal fluctuations.

Contribution

It provides a detailed analysis of melting mechanisms in irregular 2D Coulomb systems, highlighting the role of defect proliferation and bond-orientational order loss.

Findings

Solid-like phase with bond-orientational order at low temperatures

Melting driven by defect proliferation and loss of bond order

Smooth crossover from solid-like to liquid-like phase with increasing temperature

Abstract

The "melting" of self-formed rigid structures made of a small number of interacting classical particles confined in an irregular two-dimensional space is investigated using Monte Carlo simulations. It is shown that the interplay of long-range Coulomb repulsions between these particles and the irregular confinement yields a solid-like phase at low temperatures that possesses a bond-orientational order, however, the positional order is depleted even at the lowest temperatures. Upon including thermal fluctuations, this solid-like phase smoothly crosses over to a liquid-like phase by destroying the bond-orientational order. The collapse of solidity is shown to be defect mediated, and aided by the proliferation of free disclinations. The behavior of different physical observables across the crossover region are obtained. Our results will help quantifying melting found in experiments on systems with confined geometries.