Optically initialized robust valley-polarized holes in monolayer WSe2

Wei-Ting Hsu, Yen-Lun Chen, Chiang-Hsiao Chen, Pang-Shiuan Liu, Tuo-Hung Hou, Lain-Jong Li, Wen-Hao Chang

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112 Scopus citations

Abstract

A robust valley polarization is a key prerequisite for exploiting valley pseudospin to carry information in next-generation electronics and optoelectronics. Although monolayer transition metal dichalcogenides with inherent spin–valley coupling offer a unique platform to develop such valleytronic devices, the anticipated long-lived valley pseudospin has not been observed yet. Here we demonstrate that robust valley-polarized holes in monolayer WSe2 can be initialized by optical pumping. Using time-resolved Kerr rotation spectroscopy, we observe a long-lived valley polarization for positive trion with a lifetime approaching 1 ns at low temperatures, which is much longer than the trion recombination lifetime (~10–20 ps). The long-lived valley polarization arises from the transfer of valley pseudospin from photocarriers to resident holes in a specific valley. The optically initialized valley pseudospin of holes remains robust even at room temperature, which opens up the possibility to realize room-temperature valleytronics based on transition metal dichalcogenides.
Original languageEnglish (US)
JournalNature Communications
Volume6
Issue number1
DOIs
StatePublished - Nov 25 2015

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