Coherent stimulated amplification of the skyrmion breathing

Abstract

Magnetic skyrmions are topological solitons and have great potential applications in next-generation spintronic devices for information storage and processing technologies. Here, we present an approach using the master equation involving the thermal noise to obtain the dynamical evolution of the skyrmion breathing based on the three-magnon scattering in a magnetic film, and develop a two-step model to obtain the approximated analytic solution. We show that the skyrmion breathing experiences a process where the thermal noise competes with the time-varying gain in the step I. Then the excited magnon number of the skyrmion breathing mode undergoes exponential growth with the evolutionary time due to the generation of negative total damping rate induced by the microwave drive field in the step II, which is referred to as coherent stimulated amplification of the skyrmion breathing. The analytic result is shown to be in good agreement with numerical calculation. We also obtain the threshold power of the coherent stimulated amplification behavior. In addition to offering insight into the nonlinear dynamics of skyrmions, potential applications range from realizing skyrmion cooling to providing excitation source for PT-symmetric skyrmionic systems.