Heterogeneous dynamic behavior of skyrmions on a periodic substrate under dc and ac drives

We investigate the collective dynamics of skyrmions in a monoaxial periodic substrate under dc and ac drives, based on the Thiele approach. Despite the repulsive interaction between skyrmions, clustering behavior and a complex-oriented dimers phase emerge when a dc drive is applied along the substrate-periodicity direction, and the phase diagram is depicted. Further, for a dc drive perpendicular to the substrate-periodicity direction, anomalous transport behaviors under an additional perpendicular or parallel ac drive are detected, including negative mobility and negative differential conductivity. The underlying mechanism of these anomalous transports is explored. The skyrmion Hall effect plays a crucial role in all these dynamic behaviors. In this study, we provide understanding of the heterogeneous behaviors of skyrmions which are important both theoretically and experimentally.