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arXiv · 2509.05620

Quantization of spin circular photogalvanic effect in altermagnetic Weyl semimetals

Hiroki Yoshida·Jan Priessnitz·Libor Šmejkal·Shuichi Murakami
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Abstract

We theoretically predict a spin-current analog of the quantized circular photogalvanic effect in Weyl semimetals. This phenomenon is forbidden in antiferromagnets by symmetry but uniquely allowed in altermagnets, highlighting a novel and intrinsic characteristic of altermagnetism. To systematically explore second-order spin current responses, we classify all symmetry-allowed responses based on spin point groups. Furthermore, we provide a comprehensive classification of altermagnetic Weyl semimetals by identifying spin space groups that host symmetry-enforced Weyl points. Utilizing this classification, we construct a symmetry-guided tight-binding model and confirm our predictions. Finally, we identify Weyl crossings in a material candidate via first-principle calculations. Our work unveils a distinctive optical response of altermagnets, paving the way for a new frontier in altermagnetism.

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Hiroki Yoshida, Jan Priessnitz, Libor Šmejkal, Shuichi Murakami. 2025-09-06. Quantization of spin circular photogalvanic effect in altermagnetic Weyl semimetals. https://doi.org/10.1103/463y-q7lt

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