2026-05-21 東京科学大学
図1. フェロアキシャル秩序を持つ結晶におけるラマン光学活性（ROA）の模式図。
＜関連情報＞
- https://www.isct.ac.jp/ja/news/ati2jkvlcrqd#top
- https://journals.aps.org/prl/abstract/10.1103/wrv8-4f7k
NiTiO₃におけるフェロ軸秩序によって誘起されるラマン光学活性 Raman Optical Activity Induced by Ferroaxial Order in NiTiO3
Gakuto Kusuno, Takeshi Hayashida, Takayuki Nagai, Hikaru Watanabe, Rikuto Oiwa, Tsuyoshi Kimura, and Takuya Satoh
Physical Review Letters Published: 19 May, 2026
DOI: https://doi.org/10.1103/wrv8-4f7k
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 nonmagnetic ferroaxial crystal. Using circularly polarized Raman spectroscopy on single-crystalline NiTiO3, 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.
