Two-Dimensional van der Waals Superconductor Heterostructures: Josephson Junctions and Beyond.

The past few years have witnessed prominent progress in two-dimensional (2D) van der Waals heterostructures. Vertically assembled in an artificial manner, these atomically thin layers possess distinctive electronic, magnetic, and other properties, which have provided a versatile platform for both fundamental exploration and practical applications in condensed matter physics and materials science. Within various potential combinations, a particular set of van der Waals superconductor (SC) heterostructures, which is realized by stacking fabrication based on two-dimensional SCs, is currently attracting intense attention. For example, the Josephson junction, a specific structure in which a nonsuperconducting barrier is inserted between two proximity-coupled SCs, shows phenomena and outstanding properties with atomic-scale thickness. In this Perspective, we first review this emerging research area of van der Waals SC heterostructures, especially progress on the 2D van der Waals Josephson junctions, from the aspects of preparation, performance, and application, and also propose our vision for the future direction and potential innovation opportunities.