Unconventional superconductivity in graphene bilayers

Much of the appeal of the two-dimensional materials zoo—which includes graphene, hexagonal boron nitride, molybdenum disulfide, and many others—lies in the multitude of ways the atomically thin sheets can be stacked and combined to create new structures with novel properties. (See the article by Pulickel Ajayan, Philip Kim, and Kaustav Banerjee, Physics Today, September 2016, page 38.) Compounding the number of potential arrangements is the possibility of tuning the twist angle between successive layers. Now MIT’s Pablo Jarillo-Herrero and colleagues have shown that the twist angle between two sheets of graphene can be exploited to dramatic effect: At a so-called magic angle of approximately 1.1°, the two-layer stack becomes a superconductor.