Key Finding
Researchers at Institute of Science Tokyo (Science Tokyo) have observed Raman optical activity (ROA) in a crystal that is neither chiral nor magnetic. The effect is attributed to ferroaxial order—a coordinated rotational distortion of atoms within the lattice.
Study Details
The study was led by Professor Takuya Satoh from the Department of Physics, Science Tokyo, with collaborators from The University of Tokyo and Hokkaido University. The work was published in Physical Review Letters on May 19, 2026, and was selected as an Editors' Suggestion.
The material studied was nickel titanium oxide (NiTiO₃), which is centrosymmetric and nonmagnetic.
- Using circularly polarized Raman spectroscopy, the team detected a difference in scattered light intensity between left- and right-circularly polarized light—a signature of ROA.
- The effect reversed when measurements were taken from opposite sides of the crystal, indicating dependence on the direction of internal rotational order rather than chirality.
- The ROA signal was strongest at 785 nm wavelength, where light resonates with electronic transitions in nickel ions.
"We demonstrated for the first time that ROA can arise in a centrosymmetric and nonmagnetic crystal, overturning the conventional view that ROA requires either structural chirality or magnetic order."
— Professor Takuya Satoh, Science Tokyo
Significance
This finding challenges the conventional view that ROA requires structural chirality or magnetic order. It suggests that ferroaxial order can produce chirality-like optical responses, expanding the scope of optical techniques for materials discovery.
Key Takeaways
- First observation of Raman optical activity in a centrosymmetric, nonmagnetic crystal.
- Mechanism: Ferroaxial order creates a chirality-like optical response.
- Impact: Opens new avenues for using optical methods to identify hidden order in materials.