Nonlinear dynamics of directly coupled skyrmions in ferrimagnetic spin torque nano-oscillators

Nonlinear spin torque nano-oscillators have received substantial attentions due to their important applications in microwave communication and neuromorphic computing. Here we investigate the dynamical behaviors of directly coupled skyrmion oscillators in a synthetic ferrimagnet. We demonstrate through the micromagnetic simulation and Thiele’s equation that the skyrmion oscillators can present either synchronization or frequency comb, depending on the strength of interactions between the skyrmions. The underlying physics of the transition between the two scenarios are unveiled based on a quantitative analysis of the effective potentials, which also successfully interprets the dependence of the transition on parameters. By further demonstrating the tunability of the nonlinear dynamics by the driving current of the oscillators, our work reveals the great potentials of ferrimagnetic-skyrmion-based interacting oscillators for nonlinear applications.