2025-06-12 ノースウェスタン大学
An optical microscope image of a representative crystal that possesses centrosymmetry, yet shows differential absorption of circularly polarized light. The crystal is made of lithium, cobalt, selenium and oxygen, with the cobalt giving rise to the crystal’s purple color. Image by Kendall Kamp/Northwestern University
＜関連情報＞
- https://news.northwestern.edu/stories/2025/06/symmetrical-crystals-can-absorb-light-asymmetrically/
- https://www.science.org/doi/10.1126/science.adr5478
中心対称結晶による円偏光の差分吸収 Differential absorption of circularly polarized light by a centrosymmetric crystal
Katherine A. Parrish, Andrew Salij, Kendall R. Kamp, Evan Smith, […] , and Roel Tempelaar
Science Published:12 Jun 2025
Editor’s summary
For nearly two centuries, chemists have relied on absorption and rotation of polarized light to distinguish chiral compounds, so much so that the term “optically active” is often used synonymously with the structural absence of mirror or inversion symmetry. Parrish et al. now report that a particular centrosymmetric crystalline solid, a lithium cobalt selenium oxide compound, can nonetheless differentially absorb circularly polarized light. They explain the observation as an interference effect between linear dichroism and linear birefringence, and they derive the general symmetry requirements distinguishing the response from conventional optical activity. —Jake S. Yeston
Abstract
Crystalline solids are governed by universal structure-property relationships derived from their crystal symmetry, leading to paradigmatic rules on what properties they can and cannot exhibit. A long-held structure-property relationship is that centrosymmetric crystals cannot differentially absorb circularly polarized light. In this study, we demonstrate the design, synthesis, and characterization of the centrosymmetric material Li2Co3(SeO3)4, which violates this relationship not by defying symmetry-imposed selection rules but by invoking a photophysical process not previously characterized for crystalline solids. This process originates from an interference between linear dichroism and linear birefringence, referred to as LD-LB, and involves strong chiroptical signals that invert upon sample flipping. In addition to enabling a chiroptical response under centrosymmetry, this process opens up photonic engineering opportunities based on crystalline solids.
