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.
@article{arxiv.1705.10988,
title = {Valley Dynamics of Excitons in Monolayer Dichalcogenides},
author = {Gerd Plechinger and Philipp Nagler and Ashish Arora and Robert Schmidt and Alexey Chernikov and John Lupton and Rudolf Bratschitsch and Christian Schüller and Tobias Korn},
journal= {arXiv preprint arXiv:1705.10988},
year = {2017}
}