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Resonantly excited exciton dynamics in two-dimensional MoSe2 monolayers

Scarpelli, Lorenzo, Masia, Francesco, Alexeev, E. M., Withers, F., Tartakovskii, A. I., Novoselov, K. S. and Langbein, Wolfgang Werner 2017. Resonantly excited exciton dynamics in two-dimensional MoSe2 monolayers. Physical Review B 96 (4) , 045407. 10.1103/PhysRevB.96.045407

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Abstract

We report on the exciton and trion density dynamics in a single layer of MoSe2, resonantly excited and probed using three-pulse four-wave mixing (FWM), at temperatures from 300 K to 77 K. A multiexponential third-order response function for amplitude and phase of the heterodyne-detected FWM signal including four decay processes is used to model the data. We provide a consistent interpretation within the intrinsic band structure, not requiring the inclusion of extrinsic effects. We find an exciton radiative lifetime in the subpicosecond range consistent to what has been recently reported by Jakubczyk et al. [Nano Lett. 16, 5333 (2016)]. After the dominating radiative decay, the remaining exciton density, which has been scattered from the initially excited direct spin-allowed radiative state into dark states of different nature by exciton-phonon scattering or disorder scattering, shows a slower dynamics, covering 10-ps to 10-ns time scales. This includes direct spin-allowed transitions with larger in-plane momentum, as well as indirect and spin-forbidden exciton states. We find that exciton-exciton annihilation is not relevant in the observed dynamics, in variance from previous finding under nonresonant excitation. The trion density at 77 K reveals a decay of the order of 1 ps, similar to what is observed for the exciton. After few tens of picoseconds, the trion dynamics resembles the one of the exciton, indicating that trion ionization occurs on this time scale.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Publisher: American Physical Society
ISSN: 2469-9950
Funders: EPSRC
Date of First Compliant Deposit: 10 July 2017
Date of Acceptance: 8 June 2017
Last Modified: 25 Feb 2019 22:21
URI: http://orca-mwe.cf.ac.uk/id/eprint/102244

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