New crystal discovery could transform screens and sensors
For years, scientists believed they had a clear understanding of how crystals interact with light.
But a new discovery by researchers at Northwestern University and the University of Wisconsin-Madison has turned that idea on its head.
The team found that a special type of crystal—previously thought to be completely symmetrical and incapable of showing chiral behavior—can actually absorb light in a one-sided, “twisted” way.
This unexpected finding could lead to new technology in fields like optical displays, sensors, and secure communication.
Crystals are typically grouped and studied based on their symmetry.
One category, called centrosymmetric crystals, is symmetrical in every direction from a central point. Scientists had long believed these crystals could not display chirality, a property where something behaves differently than its mirror image.
Think of a pair of shoes—your left shoe doesn’t fit your right foot. That’s chirality. Most everyday objects, like a ball, are achiral because their mirror images are identical.
Until now, only non-centrosymmetric materials were known to interact with chiral light—light that spins like a corkscrew, either to the left or the right. The assumption was that centrosymmetric crystals would absorb both types of spinning light equally.
But in this new study, published in Science, researchers showed that under certain conditions, a centrosymmetric crystal made of lithium, cobalt, and selenium oxide absorbed one direction of spinning light more than the other. In other words, the crystal acted chiral—even though its structure is perfectly symmetrical.
“This discovery is surprising to many in the scientific community who, for a long time, thought this principle was impossible,” said Roel Tempelaar, a chemistry professor at Northwestern who helped lead the study. “We’re realizing there’s more to these crystals than we thought.”
The breakthrough started with theoretical work. Tempelaar’s team used advanced computer models to see if their past research on molecular chirality could apply to crystals. Their simulations showed it was possible for a centrosymmetric crystal to display this unusual light-absorbing behavior.
To test the theory, the team synthesized the crystal and studied how it interacted with circularly polarized light. As predicted, the crystal absorbed one direction of light more than the other—something no centrosymmetric material had ever been shown to do before.
This unexpected behavior has big implications. By unlocking new ways to control light using common materials, scientists may be able to design better screens, more accurate sensors, and faster light-based communication systems. It also opens the door to re-examining many other materials once thought to be limited by their symmetry.
As Tempelaar said, “Sometimes, there’s more than meets the eye—even in something as well-studied as a crystal.”
Source: Northwestern University.
