Control of the orbital character of indirect excitons in MoS2/WS2 heterobilayers

Valley selective hybridization and residual coupling of electronic states in commensurate van der Waals (vdW) heterobilayers enable the control of the orbital character of interlayer excitons. We demonstrate electric field control of layer index, orbital character, lifetime, and emission energy of indirect excitons in ${\mathrm{MoS}}_{2}/{\mathrm{WS}}_{2}$ heterobilayers embedded in an vdW field-effect structure. Different excitonic dipoles normal to the layers are found to stem from bound electrons and holes located in different valleys of ${\mathrm{MoS}}_{2}/{\mathrm{WS}}_{2}$ with a valley selective degree of hybridization. For the energetically lowest emission lines, coupling of electronic states causes a field-dependent level anticrossing that goes along with a change of the interlayer exciton lifetime from 400 to 100 ns. In the hybridized regime the exciton is delocalized between the two constituent layers, whereas for large positive or negative electric fields, the layer index of the bound hole is field dependent. Our results demonstrate the design of van der Waals solids with the possibility to $\mathit{in}$ situ control their physical properties via external stimuli such as electric fields.