Hall Effect Induced by Topologically Trivial Target Skyrmions

TL;DR

This paper demonstrates that a topologically trivial target skyrmion can induce a Hall effect, challenging the belief that a nonzero skyrmion number is necessary for such phenomena, supported by semiclassical and quantum analyses.

Contribution

It shows that topologically trivial target skyrmions can produce a Hall effect, expanding understanding beyond topological spin textures.

Findings

Hall signal is nonmonotonic with energy and skyrmion radius

Quantum treatment confirms semiclassical results

Hall effect does not require nonzero skyrmion number

Abstract

Electrons moving through a noncoplanar magnetic texture acquire a Berry phase, which can be described as an effective magnetic field. This effect is known as the topological Hall effect and has been observed in topological spin textures. Motivated by recent experimental realizations, here we study the Hall effect in a nontopological magnetic texture known as a target skyrmion. We start from a simplified semiclassical picture and show that the Hall signal is a nonmonotonic function of both the electronic energy and target skyrmion radius. That observation carries over to the fully quantum mechanical treatment in a Landauer-B\"uttiker formalism in a mesoscopic setting. Our conclusion challenges the popular opinion in the community that the Hall effect in such structures necessarily requires a nonzero skyrmion number.