Diffusion asymmetry of repulsive skyrmions in structured environment

The diffusion of matter in structured environments can give rise to emergent phenomena that do not occur in unstructured environments. Here, we report the asymmetric diffusion of magnetic skyrmions in structured chambers, where repulsive skyrmion-skyrmion and skyrmion-environment interactions play vital roles in their diffusive behavior. By fabricating an off-center asymmetric gate separating two chambers, skyrmions could demonstrate asymmetric diffusion through the gate, which depends on the gate symmetry, the gate opening width, and the skyrmion density. Although the diffusion is affected by the skyrmion density, the simulation outcomes are generally in line with rate equation solutions assuming time-independent diffusion rates. Diffusive skyrmions within the chamber can transiently form bonds through repulsive skyrmion-skyrmion interactions, leading to emergent rotational dynamics that is unique to interacting skyrmion systems. Our results uncover asymmetric diffusive behavior of skyrmions, offering insights that will appeal to the wide audience interested in magnetism, active matter, and statistical physics.