PHYSORG
Artist’s impression of a string-net of light and electrons. String-nets are a theoretical kind of topologically ordered matter.
Forget solid, liquid, and gas: there are in fact more than 500 phases of matter. In a major paper in today’s issue of Science, Perimeter Faculty member Xiao-Gang Wen reveals a modern reclassification of all of them. Using modern mathematics, Wen and collaborators reveal a new system which can, at last, successfully classify symmetry-protected phases of matter. Their new classification system will provide insight about these quantum phases of matter, which may in turn increase our ability to design states of matter for use in superconductors or quantum computers. This paper, titled, “Symmetry-Protected Topological Orders in Interacting Bosonic Systems,” is a revealing look at the intricate and fascinating world of quantum entanglement, and an important step toward a modern reclassification of all phases of matter.
Condensed matter physics – the branch of physics responsible for discovering and describing most of these phases – has traditionally classified phases by the way their fundamental building blocks – usually atoms – are arranged. The key is something called symmetry. To understand symmetry, imagine flying through liquid water in an impossibly tiny ship: the atoms would swirl randomly around you and every direction – whether up, down, or sideways – would be the same. The technical term for this is “symmetry” – and liquids are highly symmetric. Crystal ice, another phase of water, is less symmetric. If you flew through ice in the same way, you would see the straight rows of crystalline structures passing as regularly as the girders of an unfinished skyscraper. Certain angles would give you different views. Certain paths would be blocked, others wide open. Ice has many symmetries – every “floor” and every “room” would look the same, for instance – but physicists would say that the high symmetry of liquid water is broken.
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