Two-dimensional transition-metal dichalcogenide materials: Toward an age of atomic-scale photonics

Two-dimensional (2D) transition-metal dichalcogenides (TMDCs) such as MoS2, WS2, MoSe2, and WSe2 present an unprecedented excitonic materials family. These materials promise to open up a new age of atomic-scale photonics where devices can be scaled down to the truly atomic level and provide novel functionalities that cannot be obtained with conventional materials systems. Knowledge of the exciton dynamics in these materials is key to the development of the photonic devices. This article reviews recent studies on the excitonic properties of 2D TMDCs and the strategies used to manipulate the exciton dynamics. It also highlights many important scientific questions that remain to be answered for the realization of atomic-scale photonics.