Efficient brightening of momentum-indirect dark excitons in ML InSe

ORAL

Abstract

Manipulating bright and dark excitons in two-dimensional (2D) materials is a key to understanding many-body correlations of exciton and further developing exciton-mediated applications. On the one hand, bright excitons can directly couple to the light and exhibit great oscillator strengths. On the other hand, dark excitons have a much longer population lifetime and diffusion length, greatly enhancing the exciton-matter interactions. In this work, we investigated the photoluminescence of hexagonal boron nitride-encapsulated monolayer indium selenide (ML InSe). Remarkably, for the first time, we found ML InSe exhibits pronounced luminescence from the momentum-indirect dark excitons, comparable to the few-layer and bulk counterparts. The brightening of dark exciton in ML InSe is attributed to the efficient acoustic phonon-assisted recombination facilitated by strong exciton-phonon coupling and the extended wavefunction in momentum space. Moreover, the asymmetric line shape in PL spectra for atomically thin InSe can be well accounted for by a carrier localization model, reflecting the unique properties of long lifetime and diffusion length of dark excitons. These unique excitonic properties of atomically thin InSe provide potential avenues for manipulating the tightly-bound dark excitons of 2D material-based photovoltaic and photocatalytic applications.

*MOST Grant No. 110-2112-M-001-065-MY3MOST Grant No. 110-2124-M-002-012MoE Grant No. 110 L9008 and 111 L9008NSTC Grant No. 111-2112-M-002-047MOST Grant. No. 109-2112-M-001-041-MY3JSPS KAKENHI Grant No. 19H05790, 20H00354 and 21H05233

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Publication: The work is submitted to ACS Nano. It's under review.

Presenters

  • Shao-Yu Chen

    • National Taiwan University
    • Monash University

Authors

  • Shao-Yu Chen

    • National Taiwan University
    • Monash University

  • Naomi T Paylaga

    • Molecular Science Technology Program, Taiwan International Graduate Program, Academia Sinica, Taiwan

  • Chang-Ti Chou

    • Institute of Atomic and Molecular Sciences, Academia Sinica

  • Jiawei Ruan

    • University of California at Berkeley, and Lawrence Berkeley National Laboratory
    • Department of Physics, University of California, Berkeley
    • UC Berkeley

  • Chia-Chun Lin

    • Institute of Atomic and Molecular Sciences, Academia Sinica

  • Takashi Taniguchi

    • National Institute for Materials Science
    • Kyoto Univ
    • International Center for Materials Nanoarchitectonics, National Institute of Materials Science
    • Kyoto University
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-044, Japan
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science
    • National Institute for Materials Science, Japan
    • National Institute For Materials Science
    • NIMS
    • National Institute for Material Science
    • International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba, Japan
    • NIMS Japan

  • Kenji Watanabe

    • National Institute for Materials Science
    • Research Center for Functional Materials, National Institute of Materials Science
    • Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-044, Japan
    • NIMS
    • Research Center for Functional Materials, National Institute for Materials Science
    • National Institute for Materials Science, Japan
    • Research Center for Functional Materials, National Institute for Materials Science, Tsukuba, Japan
    • NIMS Japan

  • Raman Sankar

    • Inst of Physics Academia Sinica
    • Institute of Physics, Academia Sinica

  • Yang-hao Chan

    • Academia Sinica
    • Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
    • Institute of Atomic and Molecular Sciences, Academia Sinica
    • Lawrence Berkeley National Laboratory

  • Wei-Hua Wang

    • Institute of Atomic and Molecular Sciences, Academia Sinica