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arXiv · 2505.22488

Raman Optical Activity Induced by Ferroaxial Order in NiTiO$_3$

Gakuto Kusuno·Takeshi Hayashida·Takayuki Nagai·Hikaru Watanabe·Rikuto Oiwa·Tsuyoshi Kimura·Takuya Satoh
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Abstract

Raman optical activity (ROA), the dependence of Raman intensity on the circular polarization of incident and scattered light, has traditionally been observed in chiral molecules and magnetic materials, where inversion or time-reversal symmetry is broken. Here we demonstrate that ROA can also arise in a centrosymmetric and non-magnetic ferroaxial crystal. Using circularly polarized Raman spectroscopy on single-crystalline NiTiO$_3$, we observed a pronounced ROA signal in the cross-circular polarization configurations, which correlates with the ferroaxial domain structure. Our symmetry analysis, first-principles calculations of phonons, and tight-binding model calculations reveal that the natural ROA originates from the ferroaxial order and persists even within the electric dipole approximation. These results establish ROA as a powerful probe of ferroaxial order in centrosymmetric systems.

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Gakuto Kusuno, Takeshi Hayashida, Takayuki Nagai, Hikaru Watanabe, Rikuto Oiwa, Tsuyoshi Kimura, Takuya Satoh. 2025-05-28. Raman Optical Activity Induced by Ferroaxial Order in NiTiO$_3$. https://doi.org/10.1103/wrv8-4f7k

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