Excitons and Polaritons in van der Waals Heterostructures

Van der Waals semiconductors provide a platform for creating two-dimensional crystals layer-by-layer and engineering excitonic states therein with exceptional properties. As moiré lattice form in a heterobilayer, carriers can tunnel between closely-aligned bands in the two neighboring monolayers, leading to hybrid states that combine a large oscillator strength similar to intra-layer excitons and tunability of inter-layer ones. Such hybrid states are manifestations of the formation of moiré lattices. When coupled to cavities, the quantum confined nature of excitons in each moiré cell manifests as strong polariton nonlinearity, providing a potentially highly tunable system for ultra-low-power optoelectronics and quantum polaritonics.