Observation of ultralong valley lifetime in WSe2/MoS2 heterostructures

Jonghwan Kim, Chenhao Jin, Bin Chen, Hui Cai, Tao Zhao, Puiyee Lee, Salman Kahn, Kenji Watanabe, Takashi Taniguchi, Sefaattin Tongay, Michael F. Crommie, Feng Wang

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Abstract

The valley degree of freedom in two-dimensional (2D) crystals recently emerged as a novel information carrier in addition to spin and charge. The intrinsic valley lifetime in 2D transition metal dichalcogenides (TMD) is expected to be markedly long due to the unique spin-valley locking behavior, where the intervalley scattering of the electron simultaneously requires a large momentum transfer to the opposite valley and a flip of the electron spin. However, the experimentally observed valley lifetime in 2D TMDs has been limited to tens of nanoseconds thus far. We report efficient generation of microsecond-long-lived valley polarization in WSe2/MoS2 heterostructures by exploiting the ultrafast charge transfer processes in the heterostructure that efficiently creates resident holes in the WSe2 layer. These valley-polarized holes exhibit near-unity valley polarization and ultralong valley lifetime: We observe a valley-polarized hole population lifetime of more than 1 ms and a valley depolarization lifetime (that is, intervalley scattering lifetime) of more than 40 ms at 10 K. The near-perfect generation of valley-polarized holes in TMD heterostructures, combined with ultralong valley lifetime, which is orders of magnitude longer than previous results, opens up new opportunities for novel valleytronics and spintronics applications.

Original languageEnglish (US)
Article numbere1700518
JournalScience Advances
Volume3
Issue number7
DOIs
StatePublished - Jul 5 2017

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ASJC Scopus subject areas

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Cite this

Kim, J., Jin, C., Chen, B., Cai, H., Zhao, T., Lee, P., Kahn, S., Watanabe, K., Taniguchi, T., Tongay, S., Crommie, M. F., & Wang, F. (2017). Observation of ultralong valley lifetime in WSe2/MoS2 heterostructures. Science Advances, 3(7), [e1700518]. https://doi.org/10.1126/sciadv.1700518