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Exciton-exciton interactions are key to understanding non-linear optical and transport phenomena in van der Waals heterobilayers, which emerged as versatile platforms to study correlated electronic states. We present a combined theory-experiment study of excitonic many-body effects based on first-principle band structures and Coulomb interaction matrix elements. Key to our approach is the explicit treatment of the fermionic substructure of excitons and dynamical screening effects for density-induced energy renormalization and dissipation. We demonstrate that broadly assumed dipolar blue shifts are almost perfectly compensated by many-body effects, mainly by screening- induced self-energy corrections. Moreover, we identify a crossover between attractive and repulsive behavior at elevated exciton densities. Theoretical findings are supported by density-dependent observations of spectrally-narrow interlayer excitons in atomically-reconstructed, hBN-encapsulated MoSe2/WSe2 heterobilayers. Both theory and experiment show energy renormalization on a scale of a few meV even for high injection densities in the vicinity of the Mott transition. These results revise the established picture of dipolar repulsion dominating exciton-exciton interactions in van der Waals heterostructures and open up opportunities for their external design.

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• Creative Commons BY Attribution 4.0 International
  

Keyword: Exciton-exciton interactions, van der Waals, many-body effects

Date published: 2024-08-14

Publisher: American Physical Society (APS)

Journal:

• Physical Review X (ISSN: 21603308) vol. 14 issue. 3 031025

Funding:

• Japan Society for the Promotion of Science 20H00354
• Japan Society for the Promotion of Science 21H05233
• Japan Society for the Promotion of Science 23H02052
• Ministry of Education, Culture, Sports, Science and Technology
• H2020 European Research Council 772195
• Emmy Noether Initiative 287022282
• Emmy Noether Initiative 314695032
• Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter 390858490
• World Premier International Research Center Initiative
• Deutsche Forschungsgemeinschaft 443405595
• Munich Center for Quantum Science and Technology 390814868
• Alexander von Humboldt-Stiftung

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

MDR DOI:

First published URL: https://doi.org/10.1103/physrevx.14.031025

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Updated at: 2025-02-05 16:30:10 +0900

Published on MDR: 2025-02-05 16:30:11 +0900