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arXiv · 2606.06909

Circular Raman responses from angular-momentum inequivalence in CoSi

Yuki Suganuma·Gakuto Kusuno·Kohei Miyazaki·Hikaru Watanabe·Rikuto Oiwa·Ryotaro Arita·Satoshi Iwasaki·Yoshiki Yasuoka·Yusuke Kousaka·Yoshihiko Togawa·Takuya Satoh
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Abstract

Circularly polarized Raman scattering in solids exhibits distinct phenomena such as Raman optical activity (ROA) and chiral-phonon-induced frequency splitting, whose relationship has remained unclear. Here we show that these seemingly different responses can be understood within a common framework based on the inequivalence of phonon states carrying opposite crystal angular momenta. Using helicity-resolved Raman spectroscopy of the chiral crystal CoSi, we find that ROA and frequency splitting arise from different symmetry channels, namely axial multipolar symmetry and structural chirality, respectively. First-principles calculations reproduce both effects and clarify their symmetry origins. These results establish angular-momentum inequivalence as a unifying principle of circular Raman responses and link helicity-resolved Raman spectroscopy to the angular-momentum structure of chiral phonons in topological materials.

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Yuki Suganuma, Gakuto Kusuno, Kohei Miyazaki, Hikaru Watanabe, Rikuto Oiwa, Ryotaro Arita, Satoshi Iwasaki, Yoshiki Yasuoka, Yusuke Kousaka, Yoshihiko Togawa, Takuya Satoh. 2026-06-05. Circular Raman responses from angular-momentum inequivalence in CoSi. https://arxiv.org/abs/2606.06909

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