High-density carriers at a strongly coupled interface between graphene and a three-dimensional topological insulator

We report on a strongly coupled bilayer graphene-Bi2Se3 device with a junction resistance of less than 1.5 k Omega mu m(2). This device exhibits unique behavior at the interface, which cannot be attributed to either material in absence of the other. We observe quantum oscillations in the magnetoresistance of the junction, indicating the presence of well-resolved Landau levels due to hole carriers of unknown origin with a very large Fermi surface. These carriers, found only at the interface, could conceivably arise due to significant hole doping of the bilayer graphene with charge transfer on the order of 2 x 10(13) cm(-2), or due to twist-angle-dependent miniband transport.