Proximity to Tunneling crossover in van der Waals semiconductor Josephson junctions

Van der Waals heterostructures serve as versatile platforms for exploring diverse physical phenomena and practical applications. In this study, we delve into the superconducting proximity effect within NbSe₂/WSe₂/NbSe₂ Josephson junctions, where the WSe₂ semiconducting weak links vary in thickness from 3 to 18 layers. By systematically increasing the thickness of WSe₂, we identify a crossover from proximity- to tunneling-type junction around 8 layers thick, indicating a proximity effect from the superconducting NbSe₂ extends approximately 4 layers deep into the WSe₂. We substantiate this discovery through an in-depth analysis of temperature-dependent junction return currents. Furthermore, our findings are corroborated by studying the I-V characteristics, size of the induced energy gap, and IcRN products. Our results provide valuable insights into the interfacial physics and proximity effects in van der Waals material-based Josephson junctions, offering a methodology that can be applied to explore similar effects in other van der Waals heterostructures