Article Dual Action Spectroscopy Exposes the Bright and Dark Excitons of Room-Temperature WSe2

Joseph Wragg ; Luca Bolzonello ; Ludovica Donati ; Karuppasamy Pandian Soundarapandian ; Riccardo Bertini ; Seth Ariel Tongay ; Kenji Watanabe SAMURAI ORCID (National Institute for Materials Science) ; Takashi Taniguchi SAMURAI ORCID (National Institute for Materials Science) ; Frank H. L. Koppens ; Niek F. van Hulst

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Joseph Wragg, Luca Bolzonello, Ludovica Donati, Karuppasamy Pandian Soundarapandian, Riccardo Bertini, Seth Ariel Tongay, Kenji Watanabe, Takashi Taniguchi, Frank H. L. Koppens, Niek F. van Hulst. Dual Action Spectroscopy Exposes the Bright and Dark Excitons of Room-Temperature WSe2. Nano Letters. 2025, 25 (19), 7658-7664. https://doi.org/10.1021/acs.nanolett.4c06349

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(abstract)

While it’s long been accepted that the role of momentum dark excitons in the photoresponse of transition metal dichalcogenides (TMD’s) is critical, their weak optical signature has made any observation confined to cryogenic conditions. Here we surpass this limit, and expose the room temperature contributions of both bright and dark excitons to the behaviour of a TMD, WSe2, from monolayer to multilayer to bulk. To do so, we present dual action spectroscopy, a photocurrent and luminescence detected Fourier-transform excitation spectroscopy scheme to microscopically map the energy landscape of WSe2. While bright excitons naturally dominate the luminescence response of the material, dark excitons dominate the current response. Notably, the dark KK' exciton is more accessible than the ground state KΛ, while the current maps reveal a disparity in the diffusivity of the two states. This work provides the basis for a new current-detected approach to study the dynamics of dark exciton states across different materials.

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Keyword: dual action spectroscopy
, bright and dark excitons
, WSe2

Date published: 2025-05-14

Publisher: American Chemical Society (ACS)

Journal:

  • Nano Letters (ISSN: 15306984) vol. 25 issue. 19 p. 7658-7664

Funding:

  • Fundaci?n Cellex
  • European Research Council 101054846
  • FUNDACI? Privada MIR-PUIG
  • Ministerio de Ciencia, Innovaci?n y Universidades CEX2019-000910-S
  • Ministerio de Ciencia, Innovaci?n y Universidades PID2021- 123814OB-I00
  • Ministerio de Ciencia, Innovaci?n y Universidades TED2021-129241BI00
  • Generalitat de Catalunya
  • Fundaci? Joan Ribas Araquistain

Manuscript type: Publisher's version (Version of record)

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First published URL: https://doi.org/10.1021/acs.nanolett.4c06349

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Updated at: 2026-02-17 08:30:29 +0900

Published on MDR: 2026-02-16 18:00:51 +0900

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