Josephson Effect in NbS$_{2}$ van der Waals Junctions

TL;DR

This paper reports the fabrication and characterization of NbS₂/NbS₂ van der Waals Josephson junctions, revealing their superconducting properties and deviations from conventional BCS theory, which could advance 2D superconducting devices.

Contribution

It introduces a modified all-dry transfer method to create NbS₂/NbS₂ Josephson junctions and provides detailed low-temperature transport measurements of their superconducting characteristics.

Findings

Superconducting transition temperature is 5.84 K.

Critical current density reaches 3975 A/cm² at 2K.

Superconducting energy gap is 0.58 meV, smaller than BCS prediction.

Abstract

Van der Waals (vdW) Josephson junctions can possibly accelerate the development of advanced superconducting device that utilizes the unique properties of two-dimensional (2D) transition metal dichalcogenide (TMD) superconductors such as spin-orbit coupling, 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 2K. Moreover, we extract a superconducting energy gap $\Delta=0.58$ meV, which is considerably smaller than that expected from the single band s-wave Bardeen-Cooper-Schrieffer (BCS) model ($\Delta=0.89$ meV).