We study the neutral exciton energy spectrum fine structure and its spin dephasing in transition metal dichalcogenides such as ${\mathrm{MoS}}_2$. The interaction of the mechanical exciton with its macroscopic longitudinal electric field is taken into account. The splitting between the longitudinal and transverse excitons is calculated by means of the both electrodynamical approach and $\mathit{k}·\mathit{p}$ perturbation theory. This long-range exciton exchange interaction can induce valley polarization decay. The estimated exciton spin dephasing time is in the picosecond range, in agreement with available experimental data.

• Received 1 March 2014
• Revised 11 April 2014

DOI:https://doi.org/10.1103/PhysRevB.89.201302