Impact of dielectric environment on exciton binding energy in monolayer WS<sub>2</sub> and WSe<sub>2</sub>

ORAL

Abstract

The large exciton binding energy in monolayer transition metal dichalcogenides (TMDs) was determined recently. The robust excitons open a venue to explore the exciton physics such as Bose-Einstein condensation at room temperature. Recent reports further demonstrated the Coulomb engineering via dielectric environment based on a few-layer graphene. However, due to the conducting nature, quenching of optical transitions is often unavoidable. Thus, it is desirable to show the tunability using insulating dielectrics. Here we investigate the impact of dielectric environment on exciton binding energy and quasiparticle bandgap in monolayer WS2 and WSe2 by exciton Rydberg spectroscopy. The dielectric constant is systematically varied from κ = 1.49 to 3.82. We found that, with increasing κ, the exciton binding energy and quasiparticle bandgap exhibit significant reductions. We found the model using nonlocally-screened Keldysh potential captures the results very well. Our work validates the applicability of Keldysh model which can be used to design TMD-based optoelectronic devices in different dielectric media.

*Supported by Welch (F-1672), MRSEC (DMR-1720595), NSF (EFMA-1542747, DMR-1808751), AOARD (FA2386-18-1-4097). W.-T.H. acknowledges the support by MOST of Taiwan (107-2917-I-564-010).

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Presenters

  • Wei-Ting Hsu

    • Department of Physics, University of Texas at Austin, TX 78712, United States
    • Department of Physics, The University of Texas at Austin, USA

Authors

  • Wei-Ting Hsu

    • Department of Physics, University of Texas at Austin, TX 78712, United States
    • Department of Physics, The University of Texas at Austin, USA

  • Jiamin Quan

    • University of Texas at Austin
    • Department of Physics, The University of Texas at Austin
    • Department of Physics, The University of Texas at Austin, USA

  • Chun Yuan Wang

    • Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA.
    • Department of Physics, The University of Texas at Austin
    • Department of Physics, The University of Texas at Austin, USA

  • Li-Shuan Lu

    • Electrophysics, National Chiao Tung University
    • Department of Electrophysics, National Chiao Tung University
    • Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
    • Department of Electrophysics, National Chiao Tung University, Taiwan

  • Wen-Hao Chang

    • Electrophysics, National Chiao Tung University
    • Department of Electrophysics, National Chiao Tung University
    • Department of Electrophysics, National Chiao Tung University,
    • Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan
    • Department of Electrophysics, National Chiao Tung University, Taiwan

  • Xiaoqin (Elaine) Li

    • University of Texas at Austin
    • University of Texas-Austin
    • The University of Texas at Austin
    • Department of Physics and Center for Complex Quantum Systems, Univ of Texas, Austin
    • Department of Physics, University of Texas at Austin, TX 78712, United States
    • Univ of Texas, Austin
    • Department of Physics, The University of Texas at Austin
    • Department of Physics, The University of Texas at Austin, USA

  • Chih-Kang Shih

    • Department of Physics, The University of Texas at Austin, Austin, Texas, 78712, USA.
    • University of Texas at Austin
    • Physics, University of Texas at Austin
    • Department of Physics, University of Texas at Austin, TX 78712, United States
    • Department of Physics, The University of Texas at Austin
    • Department of Physics, The University of Texas at Austin, USA