Skew-scattering-induced giant antidamping spin-orbit torques: Collinear and out-of-plane Edelstein effects at two-dimensional material/ferromagnet interfaces

TL;DR

This paper reveals a microscopic mechanism for giant antidamping spin-orbit torques at 2D material/ferromagnet interfaces, driven by skew scattering, leading to novel spin-charge conversion effects like a collinear Edelstein effect.

Contribution

It introduces a nonperturbative microscopic framework that explains the origin of antidamping SOT and predicts a giant enhancement due to skew scattering in 2D interfaces.

Findings

Giant antidamping SOT enhancement in dilute disorder limit

Activation of semiclassical spin-charge conversion effects

Observation of a collinear Edelstein effect with nonequilibrium spin polarization

Abstract

Heavy metal/ferromagnet interfaces feature emergent spin-orbit effects absent in the bulk materials. Because of their inherent strong coupling between spin, charge and orbital degrees of freedom, such systems provide a platform for technologically sought-after spin-orbit torques (SOTs). However, the microscopic origin of purely interfacial antidamping SOT, especially in the ultimate atomically thin limit, has proven elusive. Here, using two-dimensional (2D) van der Waals materials as a testbed for interfacial phenomena, we address this problem by means of a microscopic framework accounting for band structure effects and impurity scattering on equal footing and nonperturbatively. A number of unconventional and measurable effects are predicted, the most remarkable of which is a giant enhancement of antidamping SOT in the dilute disorder limit induced by a robust skew scattering mechanism, which is operative in realistic interfaces and does not require magnetic impurities. The newly unveiled skew scattering mechanism activates rich semiclassical spin-charge conversion effects that have gone unnoticed in the literature, including a collinear Edelstein effect with nonequilibrium spin polarization aligned with the direction of the applied current.