Time-Reversal-Even Nonlinear Current Induced Spin Polarization

TL;DR

This paper introduces a novel second-order, time-reversal-even spin polarization mechanism in centrosymmetric nonmagnetic materials, revealing its quantum origin and potential for experimental detection and applications in nonlinear spintronics.

Contribution

It uncovers a new nonlinear spin generation effect from the anomalous spin polarizability, with first-principles predictions for various materials, expanding the scope of spintronics research.

Findings

Predicts sizable spin generation in nonmagnetic hcp metals and monolayer TiTe₂.

Identifies a quantum origin from momentum space dipole of anomalous spin polarizability.

Suggests experimental detection of the predicted spin polarizations.

Abstract

We propose a time-reversal-even spin generation in second order of electric fields, which dominates the current induced spin polarization in a wide class of centrosymmetric nonmagnetic materials, and leads to a novel nonlinear spin-orbit torque in magnets. We reveal a quantum origin of this effect from the momentum space dipole of the anomalous spin polarizability. First-principles calculations predict sizable spin generations in several nonmagnetic hcp metals, in monolayer TiTe$_{2}$, and in ferromagnetic monolayer MnSe$_{2}$, which can be detected in experiment. Our work opens up the broad vista of nonlinear spintronics in both nonmagnetic and magnetic systems.