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Trio wins Nobel for effects of topology on exotic matter

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Science  07 Oct 2016:
Vol. 354, Issue 6308, pp. 21
DOI: 10.1126/science.354.6308.21

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Summary

How is a doughnut like a coffee cup but different from a coiled spring? The riddle is key to understanding this year's Nobel Prize in Physics, which honors theorists David Thouless of the University of Washington, Seattle, Michael Kosterlitz of Brown University, and Duncan Haldane of Princeton University. The answer is that, because each has one hole, the doughnut and the coffee cup have the same topology. An infinitely pliable cup could be molded into a doughnut without tearing it. The spring, on the other hand, can be unwound into a wire, flattened into a sheet, or squished into a ball. But it cannot be smoothly deformed to a make a doughnut. Thus, it has a different "topological charge"—essentially, the number of holes. Thouless, Kosterlitz, and Haldane showed that topology is more than a mathematical abstraction. It can show up in surprising ways deep in the theory of condensed matter and can explain such odd phenomena as the ability of thin films of liquid helium to flow without any resistance or odd quantum quirks magnetism in 1D chains of quantum particles. The new Nobel laureates' work laid the foundation for perhaps the hottest subject in condensed matter physics, the study of so-called topological materials such as topological insulators, which block the flow of electricity in their interiors but allow it on their surface.