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arXiv · 2608.02393

Floquet spin-group framework and its application to light-tailored spin splitting in collinear magnets

Tongshuai Zhu·Zixuan Li·Huaiqiang Wang·Su-Huai Wei·Jiawei Ruan
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Abstract

Altermagnets combine momentum-dependent spin splitting with vanishing net magnetization, opening new opportunities for spintronics. Recent studies have shown that periodic driving by linearly or circularly polarized light, as well as by multicolor light fields, can control spin splitting in altermagnets and conventional antiferromagnets, and can even generate spin splitting patterns absent in equilibrium. Despite this progress, a unified principle connecting the dynamical symmetry of light to the symmetry of spin-split bands remains lacking, limiting the systematic design of light-induced spin structures. Here, by combining the spin group of crystals with the dynamical group of light, we establish a unified Floquet spin group framework for the study of periodically driven collinear magnets with negligible spin-orbit coupling. This framework systematically determines the allowed parity, momentum dependence, and nodal structure of spin splitting under different driving protocols. Guided by this symmetry classification, we show that odd-parity, even-parity, and mixed-parity spin splittings can be switched within the same material by tailoring the driving field. We further uncover higher-order $h$-wave and $k$-wave spin splittings in three-dimensional systems. Our work establishes a unified symmetry framework for light-controlled spin splitting and provides general principles for engineering nonequilibrium spin-band structures in altermagnets and related magnetic materials.

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Tongshuai Zhu, Zixuan Li, Huaiqiang Wang, Su-Huai Wei, Jiawei Ruan. 2026-08-03. Floquet spin-group framework and its application to light-tailored spin splitting in collinear magnets. https://arxiv.org/abs/2608.02393

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