Ultrafast valley relaxation dynamics in monolayer MoS2 probed by nonequilibrium optical techniques

作者：Dal Conte S; Bottegoni F; Pogna E A A; De Fazio D; Ambrogio S; Bargigia I; D' Andrea C; Lombardo A; Bruna M; Ciccacci F; Ferrari A C; Cerullo G; Finazzi M

来源：Physical Review B, 2015, 92(23): 235425.

DOI：10.1103/PhysRevB.92.235425

We study the exciton valley relaxation dynamics in single-layerMoS(2) 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 MoS2 valley relaxation dynamics.

• 出版日期2015-12-14