Bilayer graphene Josephson junctions with induced spin orbit coupling

Interfacial coupling of graphene with transition metal dichalcogenides (TMDs) have emerged as a way to induce enhanced spin orbit coupling in few layer graphene. In our experiment, bilayer Graphene is sandwiched between exfoliated WSe₂ (bottom) and h-BN (top) and edge contacted by means of superconducting NbTiN. We report the first study of induced superconductivity in such systems by demonstrating the Josephson effect in a series of samples of varying junction lengths (300nm to 1300nm). All measured devices are found to be in the long junction limit. By means of bottom gating, we access a wide range of densities far away from the charge neutrality point, and trace the product as a function of Thouless Energy (E_th); thereby testing the validity of standard SNS long junction diffusive limit superconducting proximity effect scaling behavior (I_cR_n = αE_th) in spin orbit coupled graphene systems. As expected from theory – a universal scaling of these parameters is observed for all devices, however with a severely reduced α than expected.