Last year, tungsten diselenide (WSe2) had its magic moment. Two independent research groups discovered "magic angles" at which two atom-thin layers of the unique semiconductor, when twisted relative to one another into what's known as a moire pattern, can superconduct electricity. Cory Dean and his colleagues at Columbia documented superconductivity at a 5° twist angle; upstate at Cornell, Jie Shan and Kin Fai Mak's team saw it at around 3.5°. Until then, graphene was the only other moire material capable of the feat.
Writing again in Nature on April 1, Dean and his colleagues fill in what happens between their observed magic angle and Cornell's. Though the initial results struck researchers as two potentially distinct types of superconductivity, they are in fact smoothly connected. "Graphene has a magic angle of 1.1°. WSe2 has a magic continuum," said Columbia physics graduate student Yinjie Guo, lead author of both Columbia Nature papers.
That wide continuum of superconducting twist angles makes WSe2 a more robust platform to explore the phenomenon than graphene, which cannot deviate by more than a tenth of a degree from its magic angle. "That's a very specific condition you have to get to, and it's been a real bottleneck," noted Dean. "Working with WSe2 is extremely reproducible, which makes it much more possible to build new theories about superconductivity."
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