Interlayer excitons in MoS/CSiH/WSheterostructures: the role of the Janus intermediate layer.

The introduction of intermediate hexagonal boron nitride (hBN) between the bilayer transition metal dichalcogenide (TMD) heterostructures has been considered an efficient approach to manipulate the interlayer excitations. However, the hBN intercalation primarily serves as a spacer to increase the interlayer distance and alter the screening, without producing a significant band offset shift. Here, we use Janus monolayer CSiH, possessing a prominent out-of-plane intrinsic dipole moment and large enough band gap, as an intercalation to build trilayer MoS/CSiH/WSheterostructures. Our calculated results by means of many-body perturbation theory reveal that the band alignment characteristics and the band gaps are dramatically altered in the presence of the CSiHmonolayer, due to the large potential drop across the interface of bilayer TMDs. By solving the Bethe-Salpeter equation, we observe the static dipole moment of the interlayer excitons (IXs) can be reversed through tuning the stacking sequence of CSiH. More importantly, the radiative lifetime of IX has been substantially prolonged in MoS/CSiH/WS, several orders of magnitude longer than that of bilayer MoS/WS, and varies between 10-10s at 0 K with different stacking sequence of CSiH. Our explorations open the feasibility of simultaneously engineering the band alignment and the dipole moment of the dipolar IXs in TMD van der Waals heterostructures, through the introduction of Janus intercalation.