Evidence for Supercurrent Quantization in Interfacial Josephson Junctions

We observe a series of discontinuities in the above gap current/voltage characteristics of highly transmissive Nb/Si superconductor/semiconductor interfaces. The bias at which each switch occurs decreases in quantized steps as a function of temperature and magnetic field. The observed step-size is the same for both dependencies. We propose that the steps correspond to supercurrent quantization through granular Josephson junctions formed near the interface.