Valley dynamics of excitons in monolayer dichalcogenides

Monolayer transition‐metal dichalcogenides (TMDCs) have recently emerged as possible candidates for valleytronic applications, as the spin and valley pseudospin are directly coupled and stabilized by a large spin splitting. In these semiconducting materials, optically excited electron–hole pairs form tightly Coulomb‐bound excitons with large binding energies. The selection rules for excitonic transitions allow for direct optical generation of a valley‐polarized exciton population using resonant excitation. Here, we investigate the exciton valley dynamics in monolayers of three different TMDCs by means of time‐resolved Kerr rotation at low temperatures. We observe pronounced differences in the valley dynamics of tungsten‐ and molybdenum‐based TMDCs, which are directly related to the opposite order of the conduction‐band spin splitting in these materials.