Skyrmion-deriven topological spin and charge Hall effects in diffusive antiferromagnetic thin films

TL;DR

This paper explores how antiferromagnetic skyrmions influence topological spin and charge Hall effects in diffusive thin films, revealing conditions for observable spin accumulation and Hall voltages that could aid in electrical detection of skyrmions.

Contribution

It provides a theoretical analysis of topological Hall effects in AFM skyrmions using Boltzmann equations, including both intrinsic and extrinsic contributions, and highlights conditions for measurable signals.

Findings

Spin accumulation can be finite at edges far from skyrmion

Topological charge Hall effect produces a measurable Hall voltage

Spin Hall current vanishes rapidly outside the skyrmion

Abstract

We investigate topological Hall effects in a metallic antiferromagnetic (AFM) thin film and/or at the interface of an AFM insulator-normal metal bilayer with a single skyrmion in the diffusive regime. To determine the spin and charge Hall currents, we employed a Boltzmann kinetic equation with both spin-dependent and spin-flip scatterings. The interaction between conduction electrons and static skyrmions is included in the Boltzmann equation via the corresponding emergent magnetic field arising from the skyrmion texture. We compute intrinsic and extrinsic contributions to the topological spin Hall effect and spin accumulation, induced by an AFM skyrmion. We show that although the spin Hall current vanishes rapidly outside the skyrmion, the spin accumulation can be finite at the edges far from the skyrmion, provided the spin diffusion length is longer than the skyrmion radius. In addition, We show that in the presence of a spin-dependent relaxation time, the topological charge Hall effect is finite and we determine the corresponding Hall voltage. Our results may help to explore antiferromagnetic skyrmions by electrical means in real materials.