Transformation of a cellular skyrmion to polyomino-like structures

TL;DR

This study demonstrates how programmable current pulses can transform a cellular skyrmion into various polyomino-like structures on an artificial grid, revealing potential for data storage and computational applications.

Contribution

It introduces a method to manipulate and transform cellular skyrmions into complex shapes using programmed current pulses, expanding the functional design space of topological spin structures.

Findings

Parallel short pulses elongate skyrmions in current direction.

Long pulses induce elongation perpendicular to current due to skyrmion Hall effect.

Sequential pulses transform skyrmions into polyomino-like shapes without losing topological charge.

Abstract

Topological spin structures with transformable shapes may have potential implications on data storage and computation. Here, we demonstrate that a square cellular skyrmion on an artificial grid pinning pattern can be manipulated by programmed current pulses. We find that parallel short pulses could result in the elongation of the skyrmion mainly in the current direction, while parallel long pulses are able to induce the elongation in the direction perpendicular to the current due to the intrinsic skyrmion Hall effect. Consequently, a programmed sequence of parallel pulses could lead to the transformation of the skyrmion to I-, L-, and Z-shaped polyomino-like structures without affecting the topological charge. In addition, we find that orthogonal pulses could lead to the transformation to more complex polyomino-like structures, including the T-shaped and irregular ones. Particularly, when a small T-shaped structure is formed, the topological charge of the system is found to be non-integer due to incomplete compensation of local topological charge densities; however, the T-shaped structure is stable on the attractive pinning pattern. Our results offer an effective way to create polyomino-like spin structures toward functional applications.