Superconducting contact to 2D transition-metal dichalcogenide superconductors

Two-dimensional transition-metal dichalcogenide superconductors have unique and desirable properties for integration with conventional superconducting circuits. These properties include the ability to form atomically clean and flat interfaces with stable tunnel barriers (such as boron nitride), increased kinetic inductance due to the atomically-thin geometry, and resilience to very high in-plane magnetic fields. Integrating 2D superconductors into superconducting circuits requires a fully superconducting contact be made between the 2D material and a conventional superconductor. By means of an in situ process of etching and angled Al evaporation, we present evidence of robust superconducting edge contact to NbSe₂ fully encapsulated by insulating hBN. A critical current density J_c = 7x10⁸ A/m² is achieved in the contacts. In a second set of samples, two contacts are connected with an Al loop to form a SQUID. A Fraunhofer pattern is observed in each of these samples, whose periodicities can be modeled by using an effective area for the SQUID loop equal to the physical loop area plus an area from the thin NbSe₂ flake that is uniformly penetrated by the applied magnetic field.