Hall Effect of Spin Waves in Frustrated Magnets

TL;DR

This paper explores a spin Hall effect in frustrated magnetic systems where spin waves generate transverse spin currents due to Berry curvature effects, drawing parallels with electronic anomalous Hall phenomena.

Contribution

It introduces a theoretical framework and a microscopic model demonstrating the existence of a spin Hall effect driven by spin chirality in frustrated magnets.

Findings

Transverse spin currents are induced by magnetic field gradients.

Spin chirality leads to Berry curvature effects causing anomalous velocities.

A microscopic model confirms the feasibility of the effect in frustrated magnets.

Abstract

We examine a possible spin Hall effect for localized spin systems with no charge degrees of freedom. In this scenario, a longitudinal magnetic field gradient induces a transverse spin current carried by spin wave excitations with an anomalous velocity which is associated with the Berry curvature raised by spin chirality, in analogy with anomalous Hall effects in itinerant electron systems. Our argument is based on a semiclassical equations of motion applicable to general spin systems. Also, a microscopic model of frustrated magnets which exhibits the anamalous spin Hall effect is presented.