Observation of Intralayer and Interlayer Excitons in Monolayered WSe₂/WS₂ Heterostructure

The atomically thin two-dimensional semiconductors of the material family of transition-metal dichalcogenides exhibit astonishing many-particle physics dominated by the formation of tightly bound planar-confined excitons due to strong in-plane Coulomb interaction. In addition to bright excitonic features, the presence of various dark excitonic states also has been experimentally observed very recently in this material family. In addition to that, a different type of exciton emerges when a van-der-Waals heterostructure is assembled by deterministically stacking two different monolayer TMDCs. Here, we demonstrate a WSe₂/WS₂ type-II heterostructure where the electrons transfer to the WS₂ layer whereas the holes transfer to the WSe₂ layer, thereby giving rise to interlayer excitons. The interlayer interaction depends on the coupling strength of the heterostructure which determines the luminescence spectrum. Such spectrum features contributions from individual layers as well as the heterobilayer configuration. These results and findings open new approaches for bandgap engineering using strongly hybridized bandstructures.