Lateral NbSe₂-Graphene Josephson Junction

In recent years, there has been a growing interest in studying the superconducting proximity coupling to topological insulators and 2D magnets to probe the rich physics in such hybrid systems and their possible applications in quantum information science. To study the proximity effect, clean and transparent interfaces are required. Here we report a method to fabricate sub-100nm length lateral Josephson junctions using a non-invasive van der Waals transfer method. We pattern trenches of controlled dimensions in the van der Waals superconductor NbSe₂ using lithography then make h-BN encapsulated NbSe₂-graphene-NbSe₂ lateral Josephson junctions using dry transfer inside a glovebox. Our junction has a low contact resistivity (R_c) of 40 ohms μm, exhibits a critical current density J_c up to 700nA μm^-1 at 300mK and an I_cR_n product approximately 20% of the NbSe₂ SC gap ∆ = 1 meV in the heavy hole regime. Subharmonic gap features due to Multiple Andreev reflections are present and exhibit a temperature dependence consistent with the SC gap of NbSe₂. We observe the Fraunhofer pattern of J_c in a magnetic field. Our next step is to extend this method to topological insulators and 2D magnets.