Boosting Exciton Transport in WSe2 by Engineering Its Photonic Substrate

Efficient transport of exciton in 2D semiconductors is of great importance for developing high-speed optoelectronic devices. However, excitons in layered transition-metal dichalcogenides, a class of 2D semiconductors, can only transport over a few hundred nanometers, due to the multiple collision with phonons and disorders. Here, we boost the transport capability of excitons in layered tungsten disulfide (WSe2) by engineering its photonic environment. Extended polaritonic states are formed between the flying interfacial photons and the tightly bounded excitons, with the Rabi splitting scaling with the square root of the layer number of WSe2. The light-mass polariton can travel several or even tens of micrometers, with its lifetime down to a femtosecond scale. Therefore, these results provide a unique route for designing high-speed polaritonic devices based on 2D semiconductors.