Josephson Effect in NbS2 van der Waals Junctions.

Abstract

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 NbS2/NbS2 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 NbS2/NbS2 Josephson junction is 5.84 K, and the critical current density reaches 3975 A/cm2 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).