Directional Locking and the Influence of Obstacle Density on Skyrmion Dynamics in Triangular and Honeycomb Arrays

TL;DR

This study numerically investigates how obstacle arrays influence skyrmion motion, revealing quantized and continuous skyrmion Hall angle variations, directional locking effects, and the impact of obstacle density and Magnus force on skyrmion trajectories.

Contribution

It demonstrates the role of obstacle array symmetry and density in controlling skyrmion directional locking and Hall angles, offering insights for skyrmion trajectory design.

Findings

Skyrmion Hall angle exhibits quantized steps and continuous variation.

Directional locking occurs at specific angles due to obstacle symmetry.

Obstacle density influences skyrmion phases and trajectories.

Abstract

We numerically examine a single skyrmion dynamics under the influence of triangular and honeycomb obstacle arrays at zero temperature. The skyrmion Hall angle $\theta_{sk}$, that is the angle between the applied external drive and the direction of the skyrmion motion, increases in quantized steps or continuously as a function of the applied drive. For the obstacle arrays studied in this work, the skyrmion exhibits two main directional locking effects, where the skyrmion motion locks with $\theta_{sk}=-30^\circ$ and $-60^\circ$. We show that these directions are privileged due to the obstacle landscape symmetry, where there are channels that the skyrmion may move with less or no obstacle collisions. Besides that, the skyrmion Hall angles can be modified by changing the obstacle density in the sample, where some dynamic phases may appear, vanish or be stimulated. This interesting behavior can be useful to guide skyrmions using regions with different obstacle densities to set the skyrmion into designed trajectories. We have also investigated for fixed obstacle densities how the phases with $\theta_{sk}=-30^\circ$ and $-60^\circ$ evolve as a function of the Magnus force, where possibilities for switching between these phases and topological selection is discussed.