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  • Letter
  • Open Access

Spectral asymmetry of phonon sideband luminescence in monolayer and bilayer WSe2

Victor Funk1, Koloman Wagner2, Edith Wietek2, Jonas D. Ziegler2, Jonathan Förste1, Jessica Lindlau1, Michael Förg1, Kenji Watanabe3, Takashi Taniguchi4 et al.

Alexey Chernikov2,5,* and Alexander Högele1,6,†

  • 1Fakultät für Physik, Munich Quantum Center, and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, Geschwister-Scholl-Platz 1, 80539 München, Germany
  • 2Departement of Physics, University of Regensburg, 93053 Regensburg, Germany
  • 3Research Center for Functional Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan
  • 4International Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
  • 5Dresden Integrated Center for Applied Physics and Photonic Materials (IAPP) and Würzburg-Dresden Cluster of Excellence ct.qmat, Technische Universität Dresden, 01062 Dresden, Germany
  • 6Munich Center for Quantum Science and Technology (MCQST), Schellingtraße 4, 80799 München, Germany

  • *alexey.chernikov@tu-dresden.de
  • †alexander.hoegele@lmu.de
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Phys. Rev. Research 3, L042019 – Published 5 November, 2021

DOI: https://doi.org/10.1103/PhysRevResearch.3.L042019

Abstract

We report an experimental study of temperature-dependent spectral line shapes of phonon sideband emission stemming from dark excitons in monolayer and bilayer WSe2. Using photoluminescence spectroscopy in the range from 4 to 100 K, we observe a pronounced asymmetry in the phonon-assisted luminescence from momentum-indirect exciton reservoirs. We demonstrate that the corresponding spectral profiles are distinct from those of bright excitons with direct radiative decay pathways. The line-shape asymmetry reflects thermal distribution of exciton states with finite center-of-mass momenta, characteristic for phonon sideband emission. The extracted temperature of the exciton reservoirs is found to generally follow that of the crystal lattice, with deviations reflecting overheated populations. The latter are most pronounced in the bilayer case and at lowest temperatures. Our results add to the understanding of phonon-assisted recombination of momentum-dark excitons and, more generally, establish means to access the thermal distribution of finite-momentum excitons in atomically thin semiconductors with indirect band gaps.

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Phys. Rev. Research 3, L042019– Published 5 November, 2021
  • Received 21 May 2021
  • Revised 28 September 2021
  • Accepted 30 September 2021
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