Josephson Effect in NbS 2 van der Waals Junctions.

van der Waals (vdW) Josephson junctions can possibly accelerate the development of an advanced superconducting device that utilizes the unique properties of two-dimensional (2D) transition metal dichalcogenide (TMD) superconductors such as spin-orbit coupling and spin-valley locking. Here, we fabricate vertically stacked NbS 2 /NbS 2 Josephson junctions using a modified all-dry transfer technique and characterize the device performance via systematic low-temperature transport measurements. The experimental results show that the superconducting transition temperature of the NbS 2 /NbS 2 Josephson junction is 5.84 K, and the critical current density reaches 3975 A/cm 2 at 2 K. Moreover, we extract a superconducting energy gap Δ = 0.58 meV, which is considerably smaller than that expected from the single band s-wave Bardeen-Cooper-Schrieffer (BCS) model (Δ = 0.89 meV).