This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Diffusion is a fundamental natural phenomenon that can be observed across a wide range of length and time scales. It plays a key role in many fields, including physics, biology and economics.
In particular, asymmetric or directional diffusion of particle systems has attracted growing interest for practical applications, including the development of unconventional artificial intelligence (AI) hardware, where it could enable nonlinear, geometry-controlled information processing. Magnetic skyrmions are topological spin textures that can behave as particle-like objects with chiral dynamics. Recent reports have shown that even tiny thermal fluctuations can drive effective diffusion of skyrmions in ultrathin magnetic films and layered heterostructures.
Some experiments have also revealed a topology-dependent sideways, wall-guided motion known as the Brownian gyromotion of skyrmions when they interact in a confined space. Magnetic skyrmions can also exhibit exotic dynamic behaviors that cannot be reproduced by common particles. Their diffusive properties have immense potential in novel information-processing applications.
However, these properties, especially in structured environments, remain largely unexplored. A research team led by professor Masahito Mochizuki and associate professor Xichao Zhang from the Department of Applied Physics at Waseda University, Japan, has shown that magnetic skyrmions can exhibit asymmetric diffusion in a structured environment. "When many repulsive skyrmions diffuse thermally inside two connected chambers separated by an off-center gate, they can pass more easily in one direction than the other within a finite time interval," explains Mochizuki.
"This establishes a new principle for controlling thermal diffusion using topology and geometry." Their study was published in npj Spintronics on July 16, 2026. To study the diffusion of skyrmions in a structured environment, the team designed a theoretical model consisting of Néel-type skyrmions confined in a nanostructured magnetic thin-film system containing two chambers linked by a narrow, off-center asymmetric gate (OAG). Their analysis showed that, despite the thermally induced random motion of magnetic skyrmions, the off-center geometry caused a clear directional imbalance in their diffusion.
Skyrmions placed in the left chamber were more likely to pass through the OAG than skyrmions approaching from the opposite side. Computational simulations with multiple repulsive skyrmions initially placed on either side of the OAG confirmed this theoretical finding. The team found that this key mechanism was not simply due to the asymmetric configuration of the gate but instead emerged from the interplay between the structured environment and the unique topology-dependent dynamics of skyrmions.
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