Fig. 1
Excitation and relaxation processes of valley-polarized excitons. a Schematic of the processes in the |+K〉 valley-pseudospin-selective excitation followed by circularly polarized PL from the bright (k ≈ 0) excitons with |+K〉 (red) or |−K〉 (black) valley pseudospins. Solid and dotted bands correspond to the singlet-like and triplet-like exciton bands, respectively. The horizontal axis corresponds to the exciton wave vector k. Exciton bands at k ≈ 0 are at the zone center in the excitonic Brillouin zone. Intervalley dark excitons have k ≠ 0. Arrows indicate the major transition and scattering pathways assumed to be involved for the phenomena considered in this study. b Symbols denoting the rates for the exciton recombination and scattering processes considered in a. Parameter γ is a phonon scattering rate constant, and n is a phonon number available for the bright–dark (B–D) transitions with the energy difference of Δbd. In the schematics of a and b, only the intervalley B–D scattering pathways are indicated for clarity. However, we do not exclude the possibility of the contribution of the intravalley B–D scattering (see Supplementary Note 1 for additional details)
