van der Waals Josephson junctions for quantum science and technology

Abstract

Josephson junctions (JJs) made out of van der Waals (vdW) materials offer a unique route to explore novel functionalities in superconducting devices such as emergent phases, anisotropic order parameters and crystalline tunnel barriers that remain inaccessible in conventional JJs. Over the past decade, vdW JJs have advanced rapidly, driven by new fabrication techniques and a diverse vdW materials library that enables the integration of materials with vastly disparate properties for scientific exploration. Beyond material diversity, vdW crystalline materials offer new control over device symmetries, enabling the realization of Hamiltonians unique to 2D systems. Furthermore, the long relaxation times of excitations in 2D heterostructures open possibilities for creating quantum sensors, with the 2D material itself acting as an efficient bus for transmitting excitations to the active sensing element. The use of vdW materials has also opened up the opportunity to explore the effect of moiré structures and topology, which could lead to potential applications in quantum computation and ultra-sensitive hybrid sensors. Although opportunities abound with vdW JJs, the challenge of scalability must be surmounted for translation into real-world devices. In this Review, we synthesize current developments in this field and offer a forward-looking roadmap. van der Waals Josephson junctions offer opportunities to explore novel device functionalities in superconducting circuits. This Review discusses progress in different device architectures and provides a roadmap outlining near-term and long-term opportunities for the field.