Skyrmion dynamics induced by surface acoustic waves in antiferromagnetic systems

Abstract

In this paper, dynamics of a magnetic skyrmion induced by linear and circular surface acoustic waves in antiferromagnetic (AFM) systems are determined. The skyrmion is considered as a rigid disk with a repulsive constant potential that scatters the surface waves. By insertion of skyrmion profile inside the AFM Lagrangian, the equation of motion could be inferred. Conservation of linear and angular momenta results in a force and torque applied to the skyrmion by surface waves. The force and torque are calculated by using the scattering concept in the Born approximation for both linear and circular polarization. By equating the time derivative of these momenta with force and torque emerged from the Born approximation, the skyrmion dynamic is determined as a coupled nonlinear differential equation. The motion of skyrmion has no Hall effect in linear waves, confirming the physics of AFM skyrmion dynamics with no Magnus force. The skyrmion shows a ratchet motion in circular waves. This dynamic emerges because circular waves can produce a small amount of torque on spin texture. The velocity is inversely proportional to the Gilbert damping, as expected for AFM systems. We found meaningful consistency between our theoretical findings and atomistic simulation. Besides, we observe that the velocity goes up with skyrmion radius. Our findings uncover a nonlinear dynamics for skyrmions in AFM systems that can be originated by coupling to acoustic waves for future studies.