@article{43b4b132904045de8bfa559a59d8de9a,
title = "Momentum-Dark Intervalley Exciton in Monolayer Tungsten Diselenide Brightened via Chiral Phonon",
abstract = "Inversion symmetry breaking and 3-fold rotation symmetry grant the valley degree of freedom to the robust exciton in monolayer transition-metal dichalcogenides, which can be exploited for valleytronics applications. However, the short lifetime of the exciton significantly constrains the possible applications. In contrast, the dark exciton could be long-lived but does not necessarily possess the valley degree of freedom. In this work, we report the identification of the momentum-dark, intervalley exciton in monolayer WSe2 through low-temperature magneto-photoluminescence spectra. Interestingly, the intervalley exciton is brightened through the emission of a chiral phonon at the corners of the Brillouin zone (K point), and the pseudoangular momentum of the phonon is transferred to the emitted photon to preserve the valley information. The chiral phonon energy is determined to be ∼23 meV, based on the experimentally extracted exchange interaction (∼7 meV), in excellent agreement with the theoretical expectation of 24.6 meV. The long-lived intervalley exciton with valley degree of freedom adds an exciting quasiparticle for valleytronics, and the coupling between the chiral phonon and intervalley exciton furnishes a venue for valley spin manipulation.",
keywords = "chiral phonon, intervalley exciton, magneto-PL, time-resolved PL, tungsten diselenide",
author = "Zhipeng Li and Tianmeng Wang and Chenhao Jin and Zhengguang Lu and Zhen Lian and Yuze Meng and Mark Blei and Mengnan Gao and Takashi Taniguchi and Kenji Watanabe and Tianhui Ren and Ting Cao and Sefaattin Tongay and Dmitry Smirnov and Lifa Zhang and Shi, {Su Fei}",
note = "Funding Information: We thank Prof. Feng Wang, Prof. Ji Feng, and Prof. Ronald Hedden for helpful discussions. We acknowledge the support by AFSOR through Grant No. FA9550-18-1-0312, and we acknowledge Micro and Nanofabrication Clean Room (MNCR) at Rensselaer Polytechnic Institute (RPI) for device fabrication. Z. Li acknowledges supports from the Shanghai Sailing Program (Grant No. 19YF1425200) and the National Natural Science Foundation for Young Scientists Fund of China (Grant No. 51902196). L.Z. acknowledges support from the National Natural Science Foundation of China (Grant Nos. 11890703 and 11574154). S.T. acknowledges support from NSF DMR-1552220 and DMR 1838443. C.J. acknowledges support from a Kavli Postdoctoral Fellowship. K.W. and T.T. acknowledge support from the Elemental Strategy Initiative conducted by the MEXT, Japan, and the CREST (JPMJCR15F3), JST. Z. Lu and D.S. acknowledge support from the US Department of Energy (DE-FG02-07ER46451) for magneto-PL work performed at the NHMFL, which is supported by NSF through NSF/DMR-1644779 and the State of Florida. T.W. and S.-F.S. acknowledge support from ACS PRF through Grant No. 59957-DNI10. Z.L. and S.-F.S. acknowledge support from the New York State Empire State Development{\textquoteright}s Division of Science, Technology, and Innovation (NYSTAR) through Focus Center-NY-RPI Contract C150117. S.-F.S. is also supported by a KIP grant from RPI and a VSP grant from NHMFL. Publisher Copyright: {\textcopyright} 2019 American Chemical Society.",
year = "2019",
month = dec,
day = "24",
doi = "10.1021/acsnano.9b06682",
language = "English (US)",
volume = "13",
pages = "14107--14113",
journal = "ACS Nano",
issn = "1936-0851",
publisher = "American Chemical Society",
number = "12",
}