Topological defect motifs in two-dimensional Coulomb clusters

TL;DR

This paper investigates the distribution and types of topological defects in finite two-dimensional Coulomb clusters confined by a parabolic potential, revealing how defect structures depend on system size and energy state.

Contribution

It introduces a detailed analysis of defect motifs in Coulomb clusters, including classification of complex defect structures and their impact on lattice order.

Findings

Defect structures vary with system size and energy state.

Presence of defect compounds like grain boundaries and rosette defects.

Metastable states show proliferation of defects destroying lattice order.

Abstract

The most energetically favourable arrangement of low-density electrons in an infinite two-dimensional plane is the ordered triangular Wigner lattice. However, in most instances of contemporary interest one deals instead with finite clusters of strongly interacting particles localized in potential traps, for example, in complex plasmas. In the current contribution we study distribution of topological defects in two-dimensional Coulomb clusters with parabolic lateral confinement. The minima hopping algorithm based on molecular dynamics is used to efficiently locate the ground- and low-energy metastable states, and their structure is analyzed by means of the Delaunay triangulation. The size, structure and distribution of geometry-induced lattice imperfections strongly depends on the system size and the energetic state. Besides isolated disclinations and dislocations, classification of defect motifs includes defect compounds --- grain boundaries, rosette defects, vacancies and interstitial particles. Proliferation of defects in metastable configurations destroys the orientational order of the Wigner lattice.