Superconducting contact and quantum interference between two-dimensional van der Waals and three-dimensional conventional superconductors

Two-dimensional van der Waals superconductors offer a range of properties advantageous for quantum information processing. Integrating these materials into the well-developed platform of aluminum-based superconducting circuits requires robust zero-resistance contacts. Here the authors introduce a simple method for fabricating such contacts between deposited Al and exfoliated few-layer NbSe${}_{2}$ and they demonstrate that the Al/NbSe${}_{2}$ interface exhibits Josephson-junction-like behavior in the presence of magnetic flux. The anomalous periodicity of the interference patterns indicates that the junction phase difference depends on the flux ${\mathrm{\ensuremath{\Phi}}}^{J\phantom{\rule{0}{0ex}}J}$ through adjacent regions of the 2D crystal which are an appreciable fraction of the size of the 2D crystal itself, in striking contrast with 3D-3D Josephson junction behavior.