Asymmetric skyrmion-antiskyrmion production in ultrathin ferromagnetic films

TL;DR

This paper investigates how spin-orbit torques in ultrathin ferromagnetic films can generate skyrmion-antiskyrmion pairs through scattering processes, revealing conditions for asymmetric production and proliferation of these topological particles.

Contribution

It provides atomistic spin dynamics simulations to understand the scattering mechanisms leading to skyrmion-antiskyrmion pair creation and their dependence on chiral interactions and spin-orbit torque components.

Findings

Pair production depends on chiral interaction strength.

Scattering processes include elastic, bound, and annihilation events.

Asymmetry in particle proliferation is observed under certain conditions.

Abstract

Ultrathin ferromagnets with frustrated exchange and the Dzyaloshinskii-Moriya interaction can support topological solitons such as skyrmions and antiskyrmions, which are metastable and can be considered particle-antiparticle counterparts. When spin-orbit torques are applied, the motion of an isolated antiskyrmion driven beyond its Walker limit can generate skyrmion-antiskyrmion pairs. Here, we use atomistic spin dynamics simulations to shed light on the scattering processes involved in this pair generation. Under certain conditions a proliferation of these particles and antiparticles can appear with a growth rate and production asymmetry that depend on the strength of the chiral interactions and the dissipative component of the spin-orbit torques. These features are largely determined by scattering processes between antiskyrmions, which can be elastic or result in bound states or annihilation.