Kohn-Luttinger superconductivity on two orbital honeycomb lattice

Yu-Ping Lin; Rahul M. Nandkishore

doi:10.1103/PhysRevB.98.214521

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Kohn-Luttinger superconductivity on two orbital honeycomb lattice

Yu-Ping Lin, Rahul M. Nandkishore

DOI 10.1103/PhysRevB.98.214521 · Physical Review B

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Abstract

Motivated by experiments on twisted bilayer graphene, we study the emergence of superconductivity from weak repulsive interactions in the Hubbard model on a honeycomb lattice, with both spin and orbital degeneracies, and with the filling treated as a tunable control parameter. The attraction is generated through the Kohn-Luttinger mechanism. We find, similar to old studies of single layer graphene, that the leading superconducting instability is in a d-wave pairing channel close to Van Hove filling and is in an f-wave pairing channel away from Van Hove filling. The d-wave pairing instability further has a twelvefold degeneracy while the f-wave pairing instability has a tenfold degeneracy. We analyze the symmetry breaking perturbations to this model. Combining this with a Ginzburg-Landau analysis, we conclude that close to Van Hove filling, a spin singlet d+id pairing state should form (consistent with several other investigations of twisted bilayer graphene), whereas away from Van Hove filling we propose an unusual spin and orbital singlet f-wave pairing state.