Trochoidal motion and pair generation in skyrmion and antiskyrmion dynamics under spin-orbit torques

TL;DR

This paper explores how spin-orbit torques induce complex motions and pair creation in skyrmions and antiskyrmions, revealing new dynamics driven by internal core deformations and symmetry considerations.

Contribution

It introduces the concept of trochoidal motion and pair generation driven by core deformations, expanding understanding of skyrmion-antiskyrmion dynamics under spin-orbit torques.

Findings

Spin-orbit torques can induce trochoidal motion in skyrmions and antiskyrmions.

Core deformations lead to time-dependent helicity affecting core motion.

The phase diagram predicts control over skyrmion dynamics and lattice formation.

Abstract

Skyrmions and antiskyrmions in magnetic ultrathin films are characterised by a topological charge describing how the spins wind around their core. This topology governs their response to forces in the rigid core limit. However, when internal core excitations are relevant, the dynamics become far richer. We show that current-induced spin-orbit torques can lead to phenomena such as trochoidal motion and skyrmion-antiskyrmion pair generation that only occurs for either the skyrmion or antiskyrmion, depending on the symmetry of the underlying Dzyaloshinskii-Moriya interaction. Such dynamics are induced by core deformations, leading to a time-dependent helicity that governs the motion of the skyrmion and antiskyrmion core. We compute the dynamical phase diagram through a combination of atomistic spin simulations, reduced-variable modelling, and machine learning algorithms. It predicts how spin-orbit torques can control the type of motion and the possibility to generate skyrmion lattices by antiskyrmion seeding.