Microwave-driven Topological Resonant Excitations of Coupled Skyrmions

TL;DR

This paper investigates how dual-frequency microwave fields can manipulate coupled Skyrmions' topological resonant excitations, revealing new modes, complex behaviors, and the importance of effective mass and frequency ratios through extended theoretical models and simulations.

Contribution

It introduces an extended Thiele's equation with an effective mass for coupled Skyrmions and demonstrates control of their resonant excitations using dual-frequency microwaves.

Findings

Identification of two coupled resonant modes in Skyrmions.

Observation of polygon-like and quasiperiodic excitations.

Agreement between extended Thiele's equation solutions and micromagnetic simulations.

Abstract

We study nonlinear dynamics of coupled Skyrmions and present a method for manipulating topological resonant excitations by a dual-frequency microwave field. Thiele's equation is extended by introducing a new effective mass associated with time derivative of topological density. Two coupled resonant modes endowed with the new effective mass are found in the coupled Skyrmions. Polygon-like resonant excitations are observed and modulated when the two modes are activated simultaneously by microwave field with commensurate frequency ratio. Quasiperiodic behavior of excitations are related to an incommensurate ratio. Numerical solutions based on the extended Thiele's equation for Skyrmion under a dual-frequency field agree well with the micromagnetic simulation results and clarify the importance of frequency value, frequency ratio of an external field and the effective mass to the polygon-like dynamics of Skyrmion. We also show the coupling between two Skyrmions can dominate their topological resonant excitations.