Proximity induced superconductivity in bilayer graphene

Proximity induced superconductivity effect occurs when graphene is connected with close enough superconducting electrodes. Observations of Andreev reflection and induced supercurrents flowing through graphene sheets have already been reported in graphene. However, these effects have not been explored in bilayer graphene so far. By applying a perpendicular electric field, it is possible to open a gap in a bilayer graphene. This can be achieved in practice by designing a top gate in addition to the usual back gate. Our devices are produced on top of sapphire wafers by using transfer techniques and standard electron-beam lithography. The bilayers are sandwiched between two atomically flat hexagonal boron nitride multilayers which are both used as gate dielectric. By inducing a band gap into a bilayer graphene connected by two superconducting leads, the supercurrent could be switched off inducing a superconductor-insulator transition.