Observation of exciton-exciton interaction mediated valley Depolarization in Monolayer MoSe2

F. Mahmood, Z. Alpichshev, Y. Lee, J. Kong, N. Gedik, Nano Letters 18 (2018) 223–228.


Journal Article | Published | English
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Abstract
The valley pseudospin in monolayer transition metal dichalcogenides (TMDs) has been proposed as a new way to manipulate information in various optoelectronic devices. This relies on a large valley polarization that remains stable over long time scales (hundreds of nanoseconds). However, time-resolved measurements report valley lifetimes of only a few picoseconds. This has been attributed to mechanisms such as phonon-mediated intervalley scattering and a precession of the valley pseudospin through electron-hole exchange. Here we use transient spin grating to directly measure the valley depolarization lifetime in monolayer MoSe2. We find a fast valley decay rate that scales linearly with the excitation density at different temperatures. This establishes the presence of strong exciton-exciton Coulomb exchange interactions enhancing the valley depolarization. Our work highlights the microscopic processes inhibiting the efficient use of the exciton valley pseudospin in monolayer TMDs.
Publishing Year
Date Published
2018-01-10
Journal Title
Nano Letters
Volume
18
Issue
1
Page
223 - 228
IST-REx-ID

Cite this

Mahmood F, Alpichshev Z, Lee Y, Kong J, Gedik N. Observation of exciton-exciton interaction mediated valley Depolarization in Monolayer MoSe2. Nano Letters. 2018;18(1):223-228. doi:10.1021/acs.nanolett.7b03953
Mahmood, F., Alpichshev, Z., Lee, Y., Kong, J., & Gedik, N. (2018). Observation of exciton-exciton interaction mediated valley Depolarization in Monolayer MoSe2. Nano Letters, 18(1), 223–228. https://doi.org/10.1021/acs.nanolett.7b03953
Mahmood, Fahad, Zhanybek Alpichshev, Yi Lee, Jing Kong, and Nuh Gedik. “Observation of Exciton-Exciton Interaction Mediated Valley Depolarization in Monolayer MoSe2.” Nano Letters 18, no. 1 (2018): 223–28. https://doi.org/10.1021/acs.nanolett.7b03953.
F. Mahmood, Z. Alpichshev, Y. Lee, J. Kong, and N. Gedik, “Observation of exciton-exciton interaction mediated valley Depolarization in Monolayer MoSe2,” Nano Letters, vol. 18, no. 1, pp. 223–228, 2018.
Mahmood F, Alpichshev Z, Lee Y, Kong J, Gedik N. 2018. Observation of exciton-exciton interaction mediated valley Depolarization in Monolayer MoSe2. Nano Letters. 18(1), 223–228.
Mahmood, Fahad, et al. “Observation of Exciton-Exciton Interaction Mediated Valley Depolarization in Monolayer MoSe2.” Nano Letters, vol. 18, no. 1, American Chemical Society, 2018, pp. 223–28, doi:10.1021/acs.nanolett.7b03953.

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