Abstract
We study the exciton valley relaxation dynamics in single-layer by a combination of two nonequilibrium optical techniques: time-resolved Faraday rotation and time-resolved circular dichroism. The depolarization dynamics, measured at 77 K, exhibits a peculiar biexponential decay, characterized by two distinct time scales of 200 fs and 5 ps. The fast relaxation of the valley polarization is in good agreement with a model including the intervalley electron-hole Coulomb exchange as the dominating mechanism. The valley relaxation dynamics is further investigated as a function of temperature and photoinduced exciton density. We measure a strong exciton density dependence of the transient Faraday rotation signal. This indicates the key role of exciton-exciton interactions in valley relaxation dynamics.
- Received 12 August 2015
- Revised 3 November 2015
DOI:https://doi.org/10.1103/PhysRevB.92.235425
©2015 American Physical Society