Solid--liquid transition of skyrmions in a two-dimensional chiral magnet

TL;DR

This paper investigates the phase transition behavior of skyrmions in a 2D chiral magnet, revealing a direct solid-to-liquid transition without an intermediate hexatic phase, using large-scale Monte Carlo simulations.

Contribution

It provides the first detailed simulation-based analysis of skyrmion melting, showing a direct transition from solid to liquid in a 2D chiral magnet system.

Findings

Skyrmions form a 2D solid with power-law positional correlations.

At higher temperature, skyrmions transition directly to a liquid phase.

No intermediate hexatic phase observed in the skyrmion melting process.

Abstract

We study the melting of skyrmions in a two-dimensional Heisenberg chiral magnet with bi-axial Dzyaloshinskii--Moriya interactions. These topological excitations may form at zero temperature a triangular crystal with long-range positional order. However, we show using large-scale Monte Carlo simulations that at small finite temperature, the skyrmions rather form a typical two-dimensional solid: Positional correlations decay with distance as power laws while the orientational correlations remain finite. At higher temperature, we observe a direct transition from this two-dimensional solid to a liquid with short-range correlations. This differs from generic two-dimensional homogeneous particle systems, where a hexatic phase is realized between the solid and the liquid.