Nb-based Josephson junctions with Bi2Sr2CaCu2O8+δ as the barrier

We fabricated Josephson junctions with two-dimensional (2D) non-superconducting Bi ₂ Sr ₂ CaCu ₂ O _8+δ (Bi-2212) crystal flakes between Nb film. We provide a solution to get clean non-superconducting Bi-2212 flakes from optimal doping, and develop a fabrication process to make such Nb/Bi-2212 flakes/Nb Josephson heterostructures. A good Fraunhofer-like critical current modulation under magnetic fields could be observed where the shape of the junction area has been taken into account, indicating a relatively homogeneous supercurrent profile through junction. Fractional Shapiro steps could be observed, suggesting some unconventional properties in such a structure. Hopefully, the potential value for novel electronic devices like the Josephson transistor will be seen in this kind of junctions. Our work has led to the development of a novel quantum device based on the two-dimensional material BSCCO, paving the way for next-generation superconducting integrated circuits utilizing 2D materials.