Curvature-induced skyrmion deformation

Abstract

Here we perform a systematic analysis of equilibrium solutions for Neel and Bloch skyrmions on a cylindrical shell and demonstrate that both experience curvature-induced deformation. Considering the curvature as a small perturbation and applying the first-order perturbation theory we decompose the deformation on the radial symmetrical and elliptical parts. The orientation of the elliptically deformed skyrmion shape depends on the skyrmion type. For Neel skyrmion, the long semi-axis of the ellipse is oriented along or perpendicularly to the cylinder generatrix depending on the signs of the curvature and the Dzyaloshinskii--Moriya interaction. In contrast, the elliptical shape of the Bloch skyrmion makes an angle $\pmπ/4$ with the generatrix. The theoretically predicted skyrmion shapes are compared to those obtained from the numerical spin-lattice simulations. Using simulations we also investigate the nonlinear regime beyond the applicability of the first-order perturbation theory. In particular, we demonstrate that Neel skyrmion can collapse for a large enough curvature.