Intrinsic Nonlinear Spin Hall Effect and Manipulation of Perpendicular Magnetization

TL;DR

This paper introduces an intrinsic nonlinear spin Hall effect that generates spin currents in nonmagnetic materials, enabling field-free control of magnetization, with theoretical development and predictions for topological metals at room temperature.

Contribution

It presents the first microscopic theory of the nonlinear spin Hall effect, linking it to band geometry and topological features, and predicts observable effects in specific materials.

Findings

Pronounced nonlinear spin Hall effects predicted in topological metals at room temperature.

The effect enables field-free switching of perpendicular magnetization.

Theoretical framework connects the effect to quantum band geometric quantities.

Abstract

We propose an intrinsic nonlinear spin Hall effect, which enables the generation of collinearly-polarized spin current in a large class of nonmagnetic materials with the corresponding linear response being symmetry-forbidden. This opens a new avenue for field-free switching of perpendicular magnetization, which is required for the next-generation information storage technology. We develop the microscopic theory of this effect, and clarify its quantum origin in band geometric quantities which can be enhanced by topological nodal features. Combined with first-principles calculations, we predict pronounced effects at room temperature in topological metals $\mathrm{PbTaSe_{2}}$ and PdGa. Our work establishes a fundamental nonlinear response in spin transport, and opens the door to exploring spintronic applications based on nonlinear spin Hall effect.