Topological Superconductivity in Twisted Multilayer Graphene

Phys Rev Lett. 2018 Aug 24;121(8):087001. doi: 10.1103/PhysRevLett.121.087001.


We study a minimal Hubbard model for electronically driven superconductivity in a correlated flat miniband resulting from the superlattice modulation of a twisted graphene multilayer. The valley degree of freedom drastically modifies the nature of the preferred pairing states, favoring spin triplet d+id order with a valley singlet structure. We identify two candidates in this class, which are both topological superconductors. These states support half-vortices carrying half the usual superconducting flux quantum hc/(4e), and have topologically protected gapless edge states.