Chiral edge currents for ac-driven skyrmions in confined pinning geometries

Abstract

We show that ac driven skyrmion lattices in a weak pinning channel confined by regions of strong pinning exhibit edge transport carried by skipping orbits while skyrmions in the bulk of the channel undergo localized orbits with no net transport. The magnitude of the edge currents can be controlled by varying the amplitude and frequency of the ac drive or by changing the ratio of the Magnus force to the damping term. We identify a localized phase in which the orbits are small and edge transport is absent, an edge transport regime, and a fluctuating regime that appears when the ac drive is strong enough to dynamically disorder the skyrmion lattice. We also find that in some cases, multiple rows of skyrmions participate in the transport due to a drag effect from the skyrmionskyrmion interactions. The edge currents are robust for finite disorder and should be a general feature of skyrmions interacting with confined geometries or inhomogeneous disorder under an ac drive. We show that similar effects can occur for skyrmion lattices at interfaces or along domain boundaries for multiple coexisting skyrmion species. The edge current effect provides a new method to control skyrmion motion, and we discuss the connection of these results with recent studies on the emergence of edge currents in chiral active matter systems and gyroscopic metamaterials.

Transport of the obstacle arrays driven by chiral active particles with temperature difference

“…We expect that our results can be generalized to irregular obstacle arrays. In addition, our results should also be relevant to the non-biological chiral active spinners including rotating colloidal systems, granular media and even skyrmions [44][45][46][47][48][49][50][51][52]. In principle our results could be readily applied to these systems as well.…”

“…Active matter has come under the spotlight of the physical and biophysical research communities and has been studied theoretically and experimentally [1][2][3][4][5][6][7][8][9][10][11][12][13]46]. Different from simple Brownian particles, whose motion is dominated by random thermal fluctuations, active particles, also known as microswimmers, are capable of directed motion.…”

Ultrafast Ratchet Dynamics of Skyrmions by Defect Engineering in Materials with Poor Conductivity Under Gigahertz Magnetic Fields

“…As shown by our results, magnetic fields of about 50 mT can trigger efficient ratchet motion along defect tracks or edges in a speed of about 100 m/s. Note, the presence of defects or edges in the skyrmion system lowers the spatial symmetry of the system, and ratchet motion of skyrmion along a defect track or edge can actually be induced by time-varying sources without time asymmetry 43,44 . The reported mechanism therefore provides a general and feasible strategy to efficiently drive skyrmion in both metallic and insulating systems based on racetrack structures.…”

Vortex guidance and transport in channeled pinning arrays

“…Large scale regions of strong pinning coexisting with weak pinning can be created using masked irradiation techniques [21][22][23][24][25][26] . In soft matter and magnetic systems, inhomogeneous pinning can appear when one part of the sample contains strong disorder and the other part of the sample contains weak disorder 27,28 . Previous work on inhomogeneous pinning has generally focused on the case when the particles are driven parallel to an easy flow direction of the pinning, which produces shear banding or gradients in the particle velocity.…”