Nonlocal Josephson Effect in Magic Angle Graphene Devices

The recent observation of superconductivity and correlated insulating states in ‘magic-angle’ twisted bilayer graphene (MATBG) featuring nearly-flat bands at twist angles close to 1.1 degrees presents a highly tunable two-dimensional (2-D) material platform capable of behaving as a metal, an insulator, or a superconductor. This tunability enables the creation of versatile quantum devices that were previously not achievable in other single material platforms. Here, we exploit the tunability of MATBG to engineer Josephson junctions and tunneling transistors all within one material, defined solely by electrostatic gates. Our multi-gated device geometry offers complete control of the weak link in the Josephson junction, with the ability to tune the barrier independently from the superconducting regions. We show that this purely 2-D MATBG Josephson junction exhibits nonlocal electrodynamics in a magnetic field, in agreement with the theory for ultrathin superconductors first proposed by J. Pearl.
Such devices that encompass versatile functions within a single material of MATBG may find applications in graphene-based tunable superconducting qubits, on-chip superconducting circuits, and electromagnetic sensing in next-generation electronics.