Skyrmions on 2D Elastic Surfaces with Fixed Boundary Frame

TL;DR

This study simulates skyrmions on fluctuating 2D membranes with no crystalline order, revealing how magnetic and mechanical interactions influence skyrmion behavior and surface tension under various strains.

Contribution

It introduces a simulation framework for skyrmions on elastic, non-crystalline 2D surfaces, analyzing the effects of magnetic fields and strains on skyrmion stability and surface tension.

Findings

Surface tension varies with magnetic field in the skyrmion phase.

Number of skyrmions changes with magnetic field, matching experimental observations.

Stripe phase is sensitive to uniaxial strain, skyrmion phase remains stable.

Abstract

We report simulation results of skyrmions on fluctuating 2D lattices, where the vertices ${\bf r}_i (\in {\bf R}^3)$ are treated as a dynamical variable and, hence, there is no crystalline structure. On the fluctuating surfaces, an external magnetic field perpendicular to the surface, Dzyaloshinskii-Moriya and ferromagnetic interactions are assumed in addition to the Helfrich-Polyakov Hamiltonian for membranes. The surface (or frame) tension $\tau$ is calculated under both isotropic and uniaxial strain conditions, and this calculation clarifies a non-trivial dependence of $\tau$ on the skyrmion, stripe, and ferromagnetic phases. We find that the variation of $\tau$ with respect to the applied magnetic field in the skyrmion phase is accompanied by a variation of the total number of skyrmions. Moreover, we find that this total number variation is qualitatively consistent with a recent experimental result for the creation/annihilation of skyrmions of 3D crystalline material under uniaxial stress conditions. It is also found that the stripe phase is significantly influenced by uniaxial strains, while the skyrmion phase remains unchanged. These results allow us to conclude that the skyrmion phase is stable even on fluctuating surfaces.