Intervalley excitons in a minimal supercell moir\'e crystal

ORAL

Abstract

It is known that a van der Waals bilayer forms a commensurate crystal only at a discrete set of twisted angles. Whenever unit cells are commensurate in real space, their corresponding Brillouin zone (BZ) are also commensurate in momentum space. This alignment facilitates coherent tunneling and leads to conductance peaks in 21.8◦ and 38.2◦ graphene bilayers even at room temperature. In this work, we study light-matter interaction in large twist angle WSe2 bilayers. We observe surprisingly strong intervalley exciton transitions assisted by phonons in 21.8◦ WSe2 bilayer while these resonances are completely absent in a 38.2◦ bilayers. This exciton-phonon coupling also leads to a large energy shift between the intervalley exciton resonances observed in reflectivity and photoluminescence spectra. The different optical spectra in these two commensurate WSe2 bilayer originate from interlayer coupling either facilitated or suppressed by parallel or anti-parallel spins.

We gratefully acknowledge funding from the NSF MRSEC DMR-2308817 and NSF ECCS- 2130552 (Z. Liu), Department of Energy, Basic Energy Science program via grant DESC0019398 (X, Liu and K. Hao), and the Welch Foundation chair F-0014 for sample preparation.

*We gratefully acknowledge funding from the NSF MRSEC DMR-2308817 and NSF ECCS- 2130552 (Z. Liu), Department of Energy, Basic Energy Science program via grant DESC0019398 (X, Liu and K. Hao), and the Welch Foundation chair F-0014 for sample preparation.

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Presenters

  • Zhida Liu

    • University of Texas at Austin

Authors

  • Zhida Liu

    • University of Texas at Austin

  • Xiaohui Liu

    • University of Texas at Austin

  • Xiangcheng Liu

    • University of Texas at Austin

  • Kai Hao

    • The University of Texas at Austin
    • University of Texas at Austin

  • Yanxing Li

    • University of Texas at Austin

  • Fan Zhang

    • University of Texas at Austin

  • Saba Arash

    • University of Texas at Austin

  • Taeran Lee

    • Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin
    • University of Texas at Austin

  • Kenji Watanabe

    • National Institute for Materials Science
    • NIMS
    • Research Center for Functional Materials, National Institute for Materials Science
    • Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • Research Center for Functional Materials, National Institute of Material Science, Tsukuba, Japan
    • National Institute of Materials Science
    • Advanced Materials Laboratory, National Institute for Materials Science

  • Takashi Taniguchi

    • National Institute for Materials Science
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science
    • Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
    • International Center for Materials Nanoarchitectonics, National Institute of Material Science, Tsukuba, Japan
    • Advanced Materials Laboratory, National Institute for Materials Science

  • Keiji Ueno

    • Department of Chemistry, Saitama University, Japan
    • Department of Chemistry, Graduate School of Science and Engineering, Saitama University
    • Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Saitama, Japan

  • Emanuel Tutuc

    • Microelectronics Research Center, Department of Electrical and Computer Engineering, The University of Texas at Austin
    • University of Texas at Austin

  • Chih-Kang Shih

    • University of Texas at Austin

  • Xiaoqin Elaine Li

    • University of Texas at Austin