Amazing stuff! Will it be confirmed or is it a fluke?
"Researchers observed optical behaviours linked to chirality in crystalline lithium cobalt selenium oxide (Li2Co3(SeO3)4), a centrosymmetric crystal that as such cannot be chiral. ‘Within the inorganic crystal community there’s been a strong sentiment that you cannot have chiroptical effects under centrosymmetry’ ...
Chirality refers to two versions of a structure – be that light, molecules or crystals – that are almost identical but cannot be superimposed on each other, just like your left and right hand. When a structure displays centrosymmetry it has lines of symmetry in every direction from a central point, ruling out any possibility of chirality. ...
Chiral materials have a chiroptical response – they rotate linearly polarised light and absorb circularly polarised light differently depending on whether it is left-or right-handed ...
As centrosymmetric crystals have no chirality in the first place, no-one expected to see chirality in their optical response at all. However, the researchers showed that centrosymmetric crystalline Li2Co3(SeO3)4 transmits more left circularly polarised light than right. ..."
From the editor's note and abstract:
"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. ...
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."
Differential absorption of circularly polarized light by a centrosymmetric crystal (no public access)
Differential Absorption of Circularly Polarized Light by a Centrosymmetric Inorganic Crystal (preprint, working paper)
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