Directed Motion of Liquid Crystal Skyrmions With Oscillating Fields

TL;DR

This study uses continuum simulations to demonstrate that liquid crystal skyrmions can be driven in controlled directions by oscillating electric fields, with their speed and direction depending on the frequency and waveform of the applied field.

Contribution

It reveals how oscillating electric fields induce shape oscillations and directed motion in liquid crystal skyrmions, including motion reversals and the role of relaxation asymmetry.

Findings

Skyrmion speed varies non-monotonically with frequency.

Motion reversals occur as the frequency changes.

Directed motion can be achieved with single or multiple frequencies.

Abstract

Using continuum simulations, we show that under a sinusoidal electric field, liquid crystal skyrmions undergo periodic shape oscillations which produce controlled directed motion. The speed of the skyrmion is non-monotonic in the frequency of the applied field, and exhibits multiple reversals of the motion as a function of changing frequency. We map out the dynamical regime diagram of the forward and reverse motion for two superimposed ac driving frequencies, and show that the reversals and directed motion can occur even when only a single ac driving frequency is present. Using pulsed ac driving, we demonstrate that the motion arises due to an asymmetry in the relaxation times of the skyrmion shape. We discuss the connection between our results and ratchet effects observed in systems without asymmetric substrates.