Ultrafast dynamics of Rydberg excitons and their optically-induced charged complexes in encapsulated WSe2 monolayers

Armando Genco; Chiara  Trovatello; Vanik A. Shahnazaryan; Oleg Dogadov; Alisson R. Cadore; Barbara L. T. Rosa; James A.  Kerfoot; Tanweer Ahmed; Osman Balci; Evgeny Alexeev; Habib Rostami; Kenji  Watanabe; Takashi Taniguchi; Sefaattin Tongay; Andrea C. Ferrari; Giulio Cerullo; Stefano Dal  Conte

doi:10.1021/acs.nanolett.4c06428

Ultrafast dynamics of Rydberg excitons and their optically-induced charged complexes in encapsulated WSe₂ monolayers

Armando Genco, Chiara Trovatello, Vanik A. Shahnazaryan, Oleg Dogadov, Alisson R. Cadore, Barbara L. T. Rosa, James A. Kerfoot, Tanweer Ahmed, Osman Balci, Evgeny Alexeev, Habib Rostami, Kenji Watanabe, Takashi Taniguchi, Sefaattin Tongay, Andrea C. Ferrari, Giulio Cerullo, Stefano Dal Conte

Research output: Contribution to journal › Article › peer-review

Abstract

Quantum confinement and reduced dielectric screening lead to strong excitonic effects in atomically thin transition metal dichalcogenides (TMDs). Encapsulation of TMD monolayers in hexagonal boron nitride (hBN) unveils the excitonic Rydberg series below the free particle bandgap. The nonequilibrium response and the dynamics of these higher order exciton states and their multiparticle complexes remain almost unexplored. Here we use ultrafast pump–probe optical microscopy to measure the dynamics of excited-state (2s) excitons in hBN-encapsulated monolayer WSe2. 2s excitons form through an ultrafast relaxation process from high-energy states and exhibit longer decay dynamics than ground state excitons due to their higher spatial extension. We detect light-induced formation of 2s trions with significant oscillator strength and faster decay dynamics than 2s excitons, attributed to an intra-excitonic Auger effect causing an additional decay channel. Our results shed light on the dynamics of excited state excitons in TMDs and their interactions with free carriers.

Original language	English
Journal	Nano Letters
Early online date	30 Apr 2025
DOIs	https://doi.org/10.1021/acs.nanolett.4c06428
Publication status	E-pub ahead of print - 30 Apr 2025

Data Availability Statement

The data that support this study will be made available in apublic repository upon publication

Funding

We acknowledge support by the European Union Marie Sklodowska-Curie Actions project ENOSIS H2020-MSCA-IF-2020-101029644, the EU’s Horizon Europe (HORIZON) research and innovation program under the Marie Skłodowska-Curie Action PIONEER (grant agreement No. 101066108), the Optica Foundation and Coherent Inc. Bernard J. Couillaud Prize, the Swedish Research Council (VR Starting Grant No. 2018-04252), JSPS KAKENHI (Grant Numbers 21H05233 and 23H02052) and World Premier International Research Center Initiative (WPI), MEXT, Japan, EU Graphene and Quantum Flagships, ERC Grants Hetero2D, GIPT, EU Grants GRAP-X, CHARM, and EPSRC Grants EP/K01711X/1, EP/K017144/1, EP/N010345/1, EP/L016087/1, EP/V000055/1, EP/X015742/1, EP/Y035275/1, the ”Basis” Foundation (Project No. 22-1-3-43-1), DOE-SC0020653 (excitonic testing on developed crystals and exfoliated samples for quality tests), NSF CBET 2330110 (environmental stability tests), Applied Materials Inc. and Lawrence Semiconductor Labs for deposition systems, European Horizon EIC Pathfinder Open program under grant agreement no. 101130384 (QUONDENSATE), European Union’s NextGenerationEU Programme with the I-PHOQS Infrastructure [IR0000016, ID D2B8D520, CUP B53C22001750006] “Integrated Infrastructure Initiative in Photonic and Quantum Sciences”, European Union─NextGenerationEU under the National Quantum Science and Technology Institute (NQSTI) Grant No. PE00000023-q-ANTHEM-CUP H43C22000870001, European Union’s NextGenerationEU Investment 1.1, PRIN 2022 PNRR HAPPY [ID P20224AWLB, CUP D53D23016720001]. This work reflects only the authors’ views, and the European Commission is not responsible for any use that may be made of the information it contains.

Funders	Funder number
GIPT
Optica Foundation
Coherent
EU’s Horizon Europe
Horizon Therapeutics
World Premier International Research Center Initiative
European Research Council
Ministry of Education, Culture, Sports, Science and Technology
H2020 Marie Skłodowska-Curie Actions	101066108
Engineering and Physical Sciences Research Council	22-1-3-43-1, EP/L016087/1, EP/X015742/1, EP/Y035275/1, EP/K017144/1, DOE-SC0020653, EP/N010345/1, EP/K01711X/1, EP/V000055/1
Japan Society for the Promotion of Science	21H05233, 23H02052
National Science Foundation	CBET 2330110
European Union Marie Sklodowska-Curie Actions	H2020-MSCA-IF-2020-101029644
European Commission	CUP B53C22001750006, IR0000016, D2B8D520
National Quantum Science and Technology Institute	PE00000023-q-ANTHEM-CUP H43C22000870001, CUP D53D23016720001
Applied Materials, Inc.	101130384
Vetenskapsrådet	2018-04252

Keywords

Rydberg excitons
semiconducting monolayers
transition metal dichalcogenides
trions
ultrafast spectroscopy

ASJC Scopus subject areas

Bioengineering
General Chemistry
General Materials Science
Condensed Matter Physics
Mechanical Engineering

Access to Document

10.1021/acs.nanolett.4c06428Licence: CC BY

Cite this

Genco, A., Trovatello, C., Shahnazaryan, V. A., Dogadov, O., Cadore, A. R., Rosa, B. L. T., Kerfoot, J. A., Ahmed, T., Balci, O., Alexeev, E., Rostami, H., Watanabe, K., Taniguchi, T., Tongay, S., Ferrari, A. C., Cerullo, G., & Conte, S. D. (2025). Ultrafast dynamics of Rydberg excitons and their optically-induced charged complexes in encapsulated WSe₂ monolayers. Nano Letters. Advance online publication. https://doi.org/10.1021/acs.nanolett.4c06428

Genco, A, Trovatello, C, Shahnazaryan, VA, Dogadov, O, Cadore, AR, Rosa, BLT, Kerfoot, JA, Ahmed, T, Balci, O, Alexeev, E, Rostami, H, Watanabe, K, Taniguchi, T, Tongay, S, Ferrari, AC, Cerullo, G & Conte, SD 2025, 'Ultrafast dynamics of Rydberg excitons and their optically-induced charged complexes in encapsulated WSe₂ monolayers', Nano Letters. https://doi.org/10.1021/acs.nanolett.4c06428

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title = "Ultrafast dynamics of Rydberg excitons and their optically-induced charged complexes in encapsulated WSe2 monolayers",

abstract = "Quantum confinement and reduced dielectric screening lead to strong excitonic effects in atomically thin transition metal dichalcogenides (TMDs). Encapsulation of TMD monolayers in hexagonal boron nitride (hBN) unveils the excitonic Rydberg series below the free particle bandgap. The nonequilibrium response and the dynamics of these higher order exciton states and their multiparticle complexes remain almost unexplored. Here we use ultrafast pump–probe optical microscopy to measure the dynamics of excited-state (2s) excitons in hBN-encapsulated monolayer WSe2. 2s excitons form through an ultrafast relaxation process from high-energy states and exhibit longer decay dynamics than ground state excitons due to their higher spatial extension. We detect light-induced formation of 2s trions with significant oscillator strength and faster decay dynamics than 2s excitons, attributed to an intra-excitonic Auger effect causing an additional decay channel. Our results shed light on the dynamics of excited state excitons in TMDs and their interactions with free carriers.",

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AU - Dogadov, Oleg

AU - Cadore, Alisson R.

AU - Rosa, Barbara L. T.

AU - Kerfoot, James A.

AU - Ahmed, Tanweer

AU - Balci, Osman

AU - Alexeev, Evgeny

AU - Rostami, Habib

AU - Watanabe, Kenji

AU - Taniguchi, Takashi

AU - Tongay, Sefaattin

AU - Ferrari, Andrea C.

AU - Cerullo, Giulio

AU - Conte, Stefano Dal

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N2 - Quantum confinement and reduced dielectric screening lead to strong excitonic effects in atomically thin transition metal dichalcogenides (TMDs). Encapsulation of TMD monolayers in hexagonal boron nitride (hBN) unveils the excitonic Rydberg series below the free particle bandgap. The nonequilibrium response and the dynamics of these higher order exciton states and their multiparticle complexes remain almost unexplored. Here we use ultrafast pump–probe optical microscopy to measure the dynamics of excited-state (2s) excitons in hBN-encapsulated monolayer WSe2. 2s excitons form through an ultrafast relaxation process from high-energy states and exhibit longer decay dynamics than ground state excitons due to their higher spatial extension. We detect light-induced formation of 2s trions with significant oscillator strength and faster decay dynamics than 2s excitons, attributed to an intra-excitonic Auger effect causing an additional decay channel. Our results shed light on the dynamics of excited state excitons in TMDs and their interactions with free carriers.

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