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

被引：87
|
作者：
Dal Conte, S. [1 ,2 ]
Bottegoni, F. [2 ]
Pogna, E. A. A. [2 ]
De Fazio, D. [3 ]
Ambrogio, S. [4 ,5 ]
Bargigia, I. [6 ]
D'Andrea, C. [2 ,6 ]
Lombardo, A. [3 ]
Bruna, M. [3 ]
Ciccacci, F. [2 ]
Ferrari, A. C. [3 ]
Cerullo, G. [1 ,2 ]
Finazzi, M. [2 ]
机构：
[1] IFN CNR, I-20133 Milan, Italy
[2] Politecn Milan, Dipartimento Fis, I-20133 Milan, Italy
[3] Univ Cambridge, Cambridge Graphene Ctr, Cambridge CB3 0FA, England
[4] Politecn Milan, Dipartimento Elettron Informat & Bioingn, I-20133 Milan, Italy
[5] IU NET, I-20133 Milan, Italy
[6] Ist Italiano Tecnol, Ctr Nano Sci & Technol PoliMi, I-20133 Milan, Italy
来源：
PHYSICAL REVIEW B | 2015年 / 92卷 / 23期
基金：
英国工程与自然科学研究理事会;
关键词：
POLARIZATION; LIFETIMES; GRAPHENE;
D O I：
10.1103/PhysRevB.92.235425
中图分类号：
T [工业技术];
学科分类号：
08 ;
摘要：
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.
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页数：6
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