Magic-Angle Twisted Bilayer Graphene

Two graphene sheets stacked and twisted relative to each other near a "magic angle" (~1.1 degrees) host flat electronic bands, in which unconventional superconductivity and Mott-like correlated insulating states emerge -- launching the field now called "twistronics." Bistritzer & MacDonald (2011), "Moire bands in twisted double-layer graphene" (PNAS 108, 12233), theoretically predicted the flat-band phenomenon at the magic angle, but did not predict superconductivity or correlated-insulator behavior specifically. Cao, Fatemi, Fang, Watanabe, Taniguchi, Kaxiras & Jarillo-Herrero (2018), "Unconventional superconductivity in magic-angle graphene superlattices" (Nature 556, 43), made the actual empirical discovery -- alongside a companion paper the same issue reporting correlated insulating behavior at half-filling -- the genuinely surprising result the field is anchored to, not something the 2011 theory itself predicted.