対称結晶が非対称的に光を吸収(Symmetrical crystals can absorb light asymmetrically)

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2025-06-12 ノースウェスタン大学

対称結晶が非対称的に光を吸収(Symmetrical crystals can absorb light asymmetrically)
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

ノースウェスタン大学らの研究により、中心対称性を持つ結晶でも円偏光を不均一に吸収できることが実証されました。従来は対称性から光に対して非選択的とされていましたが、特定のリチウム・コバルト・セレン酸化物結晶が片方の偏光を優先的に吸収することが判明。これは光のキラル制御に新たな可能性を示し、光通信やセンサー、ディスプレイ技術への応用が期待されます。

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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.

1700応用理学一般
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