Coupled pairs of Skyrmions as Active Matter with emergent self propulsion

Amazing stuff!

"... Now [researchers] have suggested an intriguing addition to the active-matter catalog: coupled pairs of skyrmions, whirlpool-like spin arrangements that emerge in certain magnetic materials. Their theoretical work shows that such skyrmion pairs might be able to move at speeds exceeding those observed in any active-matter system ..."

From the abstract:

"Self-propulsion plays a crucial role in biological processes and nanorobotics, enabling small systems to move autonomously in noisy environments.

Here, we theoretically demonstrate that a bound skyrmion-skyrmion pair in a synthetic antiferromagnetic bilayer can function as a self-propelled topological object, reaching speeds of up to a hundred million body lengths per second—far exceeding those of any known synthetic or biological self-propelled particles.

The propulsion mechanism is triggered by the excitation of back-and-forth relative motion of the skyrmions, which generates nonreciprocal gyrotropic forces, driving the skyrmion pair in a direction perpendicular to their bond.

Remarkably, thermal noise induces spontaneous reorientations of the pair and momentary reversals of the propulsion, mimicking behaviors observed in motile bacteria and microalgae."

Physics - Skyrmions as Active Matter "Pairs of skyrmions—tiny whirlpools that emerge in some magnetic materials—might be able to self-propel, a behavior reminiscent of that of active-matter systems such as motile bacteria."

Emergent Self-Propulsion of Skyrmionic Matter in Synthetic Antiferromagnets (no public access)

Emergent Self-propulsion of Skyrmionic Matter in Synthetic Antiferromagnets (preprint, open access)