A strategy for realizing van der Waals Josephson Junction Array

Abstract

Akin to transistors forming the building blocks of semiconductor technology, Josephson junctions are essential components for quantum technologies, including superconducting qubits, Josephson voltage standards, single-charge pumping circuits, and high-speed dissipation-free logic circuits. Superconducting van der Waals (vW) systems—such as twisted graphene and NbSe₂—have been proposed as alternative platforms for constructing superconducting circuits to address the noise and decoherence caused by dielectric losses, material defects, and oxide layer inhomogeneities. While scalability and uniformity remain critical technological challenges, current studies on the vW platform focus on fabricating individual Josephson junctions via sequential stacking of two few-layered flakes. To overcome these limitations, we propose a method for realising an array of junctions from the same parent NbSe₂ flakes, employing a combination of micromechanical stacking, lithographic patterning, and etching. As a proof of concept, we realise devices comprising two NbSe₂–NbSe₂ vW Josephson junctions in series. Low-temperature electrical transport measurements, conducted down to 1.5 K, provide clear evidence of the formation of multiple Josephson junctions. Furthermore, robust supercurrent rectification is observed under in-plane magnetic fields up to 4 T, whereas no such effect is detected under out-of-plane fields, consistent with the presence of magneto-chiral anisotropy—a required mechanism for supercurrent rectification—in our system. Time-domain measurements using square wave excitation further corroborate this rectification effect. The approach outlined here for fabricating junction arrays with controlled thickness and twist-angle is readily applicable to other van der Waals systems.