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

Zhipeng Li; Tianmeng Wang; Chenhao Jin; Zhengguang Lu; Zhen Lian; Yuze Meng; Mark Blei; Shiyuan Gao; Takashi Taniguchi; Kenji Watanabe; Tianhui Ren; Sefaattin Tongay; Li Yang; Dmitry Smirnov; Ting Cao; Su-Fei Shi

doi:10.1038/s41467-019-10477-6

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

Nat Commun. 2019 Jun 6;10(1):2469. doi: 10.1038/s41467-019-10477-6.

Authors

Zhipeng Li^{1

2}, Tianmeng Wang¹, Chenhao Jin³, Zhengguang Lu^{4

5}, Zhen Lian¹, Yuze Meng^{1

6}, Mark Blei⁷, Shiyuan Gao⁸, Takashi Taniguchi⁹, Kenji Watanabe⁹, Tianhui Ren¹⁰, Sefaattin Tongay⁷, Li Yang⁸, Dmitry Smirnov⁴, Ting Cao^{11

12}, Su-Fei Shi^{13

14}

Affiliations

¹ Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA.
² School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 200240, Shanghai, China.
³ Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, 14853, USA.
⁴ National High Magnetic Field Lab, Tallahassee, FL, 32310, USA.
⁵ Department of Physics, Florida State University, Tallahassee, FL, 32306, USA.
⁶ College of Physics, Nanjing University, 210093, Nanjing, China.
⁷ School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ, 85287, USA.
⁸ Department of Physics, Washington University in St. Louis, St. Louis, MO, 63136, USA.
⁹ National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
¹⁰ School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, 200240, Shanghai, China. thren@sjtu.edu.cn.
¹¹ Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA, 94305, USA. tingcao@uw.edu.
¹² Department of Materials Science and Engineering, University of Washington, Seattle, WA, 98195, USA. tingcao@uw.edu.
¹³ Department of Chemical and Biological Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA. shis2@rpi.edu.
¹⁴ Department of Electrical, Computer & Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY, 12180, USA. shis2@rpi.edu.

Abstract

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 WSe₂. 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.

Publication types

Research Support, Non-U.S. Gov't

Grants and funding

FA9550-18-1-0312/United States Department of Defense | United States Air Force | AFMC | Air Force Office of Scientific Research (AF Office of Scientific Research)/International