Antiferromagnetic skyrmion crystals: generation, topological Hall and topological spin Hall effect

TL;DR

This paper introduces a method to create stable antiferromagnetic skyrmion crystals that exhibit topological spin Hall effects and, in some cases, topological Hall effects, with potential applications in spintronics.

Contribution

It presents a general approach to generate stable AFM skyrmion crystals and explores their topological effects, expanding understanding beyond conventional skyrmion systems.

Findings

AFM-SkXs can be stabilized on honeycomb lattices.

Equivalent lattice site AFM-SkXs show a topological spin Hall effect.

Inequivalent sublattice AFM-SkXs exhibit a nonzero topological Hall effect.

Abstract

Skyrmions are topologically nontrivial, magnetic quasi-particles, that are characterized by a topological charge. A regular array of skyrmions - a skyrmion crystal (SkX) - features the topological Hall effect (THE) of electrons, that, in turn, gives rise to the Hall effect of the skyrmions themselves. It is commonly believed that antiferromagnetic skyrmion crystals (AFM-SkXs) lack both effects. In this Rapid Communication, we present a generally applicable method to create stable AFM-SkXs by growing a two sublattice SkX onto a collinear antiferromagnet. As an example we show that both types of skyrmion crystals - conventional and antiferromagnetic - exist in honeycomb lattices. While AFM-SkXs with equivalent lattice sites do not show a THE, they exhibit a topological spin Hall effect. On top of this, AFM-SkXs on inequivalent sublattices exhibit a nonzero THE, which may be utilized in spintronics devices. Our theoretical findings call for experimental realization.