Superconductivity in twisted graphene NbSe_2 heterostructures

摘要

We study the low-energy electronic structure of heterostructures formed by one sheet of graphene placed on a monolayer of NbSe2. We build a continuous low-energy effective model that takes into account the presence of a twist angle between graphene and NbSe2, and of spin-orbit coupling and superconducting pairing in NbSe2. We obtain the parameters entering the continuous model via ab initio calculations. We show that despite the large mismatch between the graphene's and NbSe2 's lattice constants, due to the large size of the NbSe2 's Fermi pockets, there is a large range of values of twist angles for which a superconducting pairing can be induced into the graphene layer. In addition, we show that the superconducting gap induced into the graphene is extremely robust to an external in-plane magnetic field. Our results show that the size of the induced superconducting gap, and its robustness against in-plane magnetic fields, can be significantly tuned by varying the twist angle.