Emerging photoluminescence from the dark-exciton phonon replica in monolayer WSe2

• Published in: Nature communications Vol. 10; no. 1; pp. 2469 - 7
• Main Authors: Li, Zhipeng, Wang, Tianmeng, Jin, Chenhao, Lu, Zhengguang, Lian, Zhen, Meng, Yuze, Blei, Mark, Gao, Shiyuan, Taniguchi, Takashi, Watanabe, Kenji, Ren, Tianhui, Tongay, Sefaattin, Yang, Li, Smirnov, Dmitry, Cao, Ting, Shi, Su-Fei
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 06.06.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 140/125; 639/301/119/1000/1018; 639/925/930/527/1819; Chirality; Circular polarization; Electric dipoles; Electron spin; Emission; Emissions; Energy; Engineering; Excitons; First principles; Graphene; Holes (electron deficiencies); Humanities and Social Sciences; Light; Luminescence; Magnetic fields; MATERIALS SCIENCE; Monolayers; multidisciplinary; Phonons; Photoluminescence; Photons; Physics; PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Science; Science & Technology - Other Topics; Science (multidisciplinary); Transition metal compounds; Tungsten; Vibrations
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-10477-6

Tungsten-based monolayer transition metal dichalcogenides host a long-lived “dark” exciton, an electron-hole pair in a spin-triplet configuration. The long lifetime and unique spin properties of the dark exciton provide exciting opportunities to explore light-matter interactions beyond electric dipole transitions. Here we demonstrate that the coupling of the dark exciton and an optically silent chiral phonon enables the intrinsic photoluminescence of the dark-exciton replica in monolayer WSe 2 . Gate and magnetic-field dependent PL measurements unveil a circularly-polarized replica peak located below the dark exciton by 21.6 meV, equal to E″ phonon energy from Se vibrations. First-principles calculations show that the exciton-phonon interaction selectively couples the spin-forbidden dark exciton to the intravalley spin-allowed bright exciton, permitting the simultaneous emission of a chiral phonon and a circularly-polarized photon. Our discovery and understanding of the phonon replica reveals a chirality dictated emission channel of the phonons and photons, unveiling a new route of manipulating valley-spin. The long lifetime and spin properties of dark excitons in atomically thin transition metal dichalcogenides offer opportunities to explore light-matter interactions beyond electric dipole transitions. Here, the authors demonstrate that the coupling of the dark exciton and an optically silent chiral phonon enables the intrinsic photoluminescence of the dark-exciton replica in monolayer WSe 2