Litvin publishes on rotation reversal symmetry
The discovery is a new type of symmetry in the structure of materials, which the researchers say greatly expands the possibilities for discovering or designing materials with desired properties. The research is expected to have broad relevance in many development efforts involving physical, chemical, biological, or engineering disciplines including, for example, the search for advanced ferroelectric ferromagnet materials for next-generation ultrasound devices and computers.
Prior to this breakthrough, scientists and engineers had five different types of symmetries to use as tools for understanding the structures of materials whose building blocks are arranged in fairly regular patterns. Four types of symmetries had been known for thousands of years–called rotation, inversion, rotation inversion, and translation–and a fifth type–called time reversal–had been discovered about 60 years ago.
The Penn State researchers have added a new, sixth, type, called rotation reversal. As a result, the number of known ways in which the components of such crystalline materials can be combined in symmetrical ways has multiplied from no more than 1,651 before to more than 17,800 now.
"We mathematically combined the new rotation-reversal symmetry with the previous five symmetries and now we know that symmetrical groups can form in crystalline materials in a much larger number of ways," said Litvin, who coauthored the study with Venkatraman Gopalan, professor of Materials Science and Engineering <http://www.matse.psu.edu/> .
"Rotation reversal is an absolutely new approach that is different in that it acts on a static component of the material's structure, not on the whole structure all at once," Litvin said. "It is important to look at symmetries in materials because symmetry dictates all natural laws in our physical universe."
The National Science Foundation provided financial support for this research through its Materials Research Science and Engineering Centers program.