Because of type-II band alignment, interlayer exciton (IX) is found in a van der Waals (vdW) heterostructure (HS) formed by two monolayers of transition-metal dichalcogenides. Manipulation of IXs is of great importance for excitonic integrated devices. Here, we demonstrate that high pressure and tensile strain can be applied to enhance and reduce interlayer coupling of WSe2/WS2 HS, respectively. High pressure induces the transform of intralayer excitons to IX, while tensile strain leads to the transform of IXs to intralayer excitons. In addition, there is a direct-to-indirect band gap transition of WSe2/WS2 HS. The interlayer distance of WSe2/WS2 HS is reduced under high pressure, but it increased under uniaxial tensile strain from first-principles calculations. The calculated band structures explain well the transformation between interlayer and intralayer excitons of WSe2/WS2 HS. This work demonstrates the exchange of interlayer and intralayer excitons and paves the way to manipulate excitons of HS for excitonic applications.
Keywords: high pressure; interlayer exciton; intralayer exciton; tensile strain; van der Waals interaction.