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

Abstract

Skyrmions and antiskyrmions in magnetic ultrathin films are characterised by\na topological charge describing how the spins wind around their core. This\ntopology governs their response to forces in the rigid core limit. However,\nwhen internal core excitations are relevant, the dynamics become far richer. We\nshow that current-induced spin-orbit torques can lead to phenomena such as\ntrochoidal motion and skyrmion-antiskyrmion pair generation that only occurs\nfor either the skyrmion or antiskyrmion, depending on the symmetry of the\nunderlying Dzyaloshinskii-Moriya interaction. Such dynamics are induced by core\ndeformations, leading to a time-dependent helicity that governs the motion of\nthe skyrmion and antiskyrmion core. We compute the dynamical phase diagram\nthrough a combination of atomistic spin simulations, reduced-variable\nmodelling, and machine learning algorithms. It predicts how spin-orbit torques\ncan control the type of motion and the possibility to generate skyrmion\nlattices by antiskyrmion seeding.\n