Tuning and exploiting interlayer coupling in two-dimensional van der Waals heterostructures.

Two-dimensional layered materials can stack into new material systems, with van der Waals interaction between the adjacent constituent layers. This stacking process of two-dimensional atomic layers creates a new degree of freedom-interlayer interface between two adjacent layers-that can be independently studied and tuned from the intralayer degree of freedom. In such heterostructures, the physical properties are largely determined by the vdW interaction between the individual layers, i.e., interlayer coupling, which can be effectively tuned by a number of means. In this review, we summarize and discuss a number of such approaches, including stacking order, electric field, intercalation, and pressure, with both their experimental demonstrations and theoretical predictions. A comprehensive overview of the modulation on structural, optical, electrical, and magnetic properties by these four approaches are also presented. We conclude this review by discussing several prospective research directions in 2D heterostructures field, including fundamental physics study, property tuning techniques, and future applications.