Charles Kane never thought he would be cavorting with topologists. “I don't think like a mathematician,” admits Kane, a theoretical physicist who has tended to focus on tangible problems about solid materials. He is not alone. Physicists have typically paid little attention to topology — the mathematical study of shapes and their arrangement in space. But now Kane and other physicists are flocking to the field.
In the past decade, they have found that topology provides unique insight into the physics of materials, such as how some insulators can sneakily conduct electricity along a single-atom layer on their surfaces.
Some of these topological effects were uncovered in the 1980s, but only in the past few years have researchers begun to realize that they could be much more prevalent and bizarre than anyone expected. Topological materials have been “sitting in plain sight, and people didn't think to look for them”, says Kane, who is at the University of Pennsylvania in Philadelphia.
Now, topological physics is truly exploding: it seems increasingly rare to see a paper on solid-state physics that doesn’t have the word topology in the title. And experimentalists are about to get even busier. A study on page 298 of this week’s Nature unveils an atlas of materials that might host topological effects1, giving physicists many more places to go looking for bizarre states of matter such as Weyl fermions or quantum-spin liquids.
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