Exciton polaritons in mixed-dimensional transition metal dichalcogenides heterostructures.

Transition metal dichalcogenides (TMDs) promise advanced optoelectronic applications thanks to their visible or near-infrared and layer-dependent bandgaps. Even more exciting phenomena happen via stacking the TMDs to form the vertical heterostructures, such as the exotic interlayer excitons in atomically rearranged bilayer TMDs, as the result of the tunable interlayer hopping of two monolayers. So far, those literature studies focus on either two-dimensional (2D) TMDs or the layered bulky three-dimensional (3D) TMDs. The mixed-dimensional TMDs remain a fundamental yet not fully appreciated curiosity. In this Letter, we have theoretically and numerically investigated the exciton polaritons in such a hybrid system composed by the nanostructured layered (3D) and monolayer (2D) TMDs. The strong coupling has been observed of the lattice mode in high index patterned 3D TMDs and exciton from the direct bandgaps of the 2D TMDs, with the tunable Rabi splitting by geometrically shaping the 3D TMDs. We believe that our mixed-dimensional system with the novel stacks of 2D/3D van der Waals heterostructures may allow for controlling the exciton transport for advanced quantum, polaritonic, and optoelectronic devices.