Light-Induced Even-Wave Spin Splittings in Nonmagnetic Centrosymmetric Systems with Spin-Orbit Coupling

TL;DR

This paper demonstrates that circularly polarized light can induce even-parity spin splitting in nonmagnetic centrosymmetric systems, linking relativistic SOC and nonrelativistic MEC mechanisms and enabling new spintronic phases.

Contribution

It introduces a novel light-driven method to generate even-parity spin splitting, bridging two fundamental mechanisms and enabling complex spin band structures in nonmagnetic materials.

Findings

Circularly polarized light induces even-parity spin splitting in centrosymmetric, nonmagnetic systems.

The symmetry of the induced splitting depends on the orbital character, allowing various wave symmetries.

The spin-split bands can host a Chern insulator phase and exhibit spin and orbital magnetization.

Abstract

Spin splitting underpins a vast range of spin-dependent phenomena. Traditionally, two primary mechanisms generate such splitting: relativistic spin-orbit coupling (SOC) and nonrelativistic magnetic exchange coupling (MEC). Governed by distinct symmetry constraints, they produce splittings of opposite parity -- odd for SOC and even for MEC -- a dichotomy that underpins the distinct spin physics of nonmagnetic and magnetic systems. In this work, we break this dichotomy by demonstrating the dynamic generation of even-parity spin splitting in centrosymmetric, nonmagnetic systems driven by circularly polarized light. We show that the symmetry of the induced splitting is controlled by the angular character of the underlying orbitals, enabling the realization of s-wave, d-wave, and g-wave spin-split band structures identical to those of ferromagnets and altermagnets. Furthermore, we find that these spin-split bands can naturally host a Chern insulator phase. We also discuss the associated spin and orbital magnetization. Our results establish a direct and previously unrecognized conceptual link between the two fundamental mechanisms of spin splitting.