Strong coupling and pressure engineering in WSe2–MoSe2 heterobilayers

Two-dimensional materials offer an exciting platform that enables the creation of van der Waals heterostructures with rich functions and intriguing physical properties that stem from different band alignments and diverse interlayer interactions. However, further exploration of two-dimensional van der Waals heterostructures is hindered by the limited coupling strength and lack of efficient methods for tuning the interlayer interactions. Here, by using a two-step chemical vapour deposition method, we realize high-quality 2H-stacked WSe2–MoSe2 heterostructures with strong interlayer coupling, and effective tuning of their interlayer interaction by hydrostatic pressure. We unambiguously establish the strong coupling nature in these WSe2–MoSe2 heterostructures through the existence of exclusive interlayer excitons instead of the typical intralayer excitons. We further demonstrate efficient tuning of the interlayer coupling by using pressure engineering, and observe a clear evolution and transition of interlayer excitons in WSe2–MoSe2 heterostructures with a pressure-induced band changeover, which is further confirmed by first-principles calculations. Our findings provide new opportunities for producing, exploring and tuning van der Waals heterostructures with strong interlayer coupling that can lead towards the realization of future excitonic devices based on tailor-made, atomically thin, two-dimensional stacks.