Vortex dynamics in 2D antiferromagnets

TL;DR

This paper investigates vortex behavior in 2D antiferromagnets, revealing scattering, annihilation, and dynamics influenced by external fields, with implications for topological excitations in magnetic systems.

Contribution

It provides a combined numerical and analytical study of vortex dynamics, including effects of bias fields and topological excitations in 2D antiferromagnets.

Findings

Like vortices scatter at 90 degrees during collisions.

Vortex-antivortex pairs annihilate into spinwave radiation.

Bias fields induce Hall and Magnus effects in vortex motion.

Abstract

The dynamics of vortices in a 2D Heisenberg antiferromagnet with an easy-plane anisotropy is studied numerically within the discrete spin model as well as analytically within a continuum approximation based on a suitable extension of the relativistic nonlinear sigma model. We find that two like vortices scatter at 90 degrees during a head-on collision, whereas a vortex-antivortex pair is annihilated into spinwave radiation emitted mainly at 90 degrees. When a uniform bias field is applied, vortex dynamics is affected rather profoundly and acquires the characteristic features of the Hall effect of electrodynamics or the Magnus effect of fluid dynamics. In particular, a single vortex is always spontaneously pinned, two like vortices form a rotating bound state, and a vortex-antivortex pair undergoes Kelvin motion. Finally, in the presence of a bias field, vortices are shown to be the prominent topological excitations even for an isotropic antiferromagnet.