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Observation of Multi-Directional Energy Transfer in a Hybrid Plasmonic-Excitonic Nanostructure.

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Hybrid plasmonic devices involve a nanostructured metal supporting localized surface plasmons to amplify light-matter interaction, and a non-plasmonic material to functionalize charge excitations. Application-relevant epitaxial heterostructures, however, give rise to ballistic ultrafast dynamics that challenge the conventional semiclassical understanding of unidirectional nanometal-to-substrate energy transfer. Epitaxial Au nanoislands are studied on WSe2 with time- and angle-resolved photoemission spectroscopy and femtosecond electron diffraction: this combination of techniques resolves material, energy, and momentum of charge-carriers and phonons excited in the heterostructure. A strong non-linear plasmon-exciton interaction that transfers the energy of sub-bandgap photons very efficiently to the semiconductor is observed, leaving the metal cold until non-radiative exciton recombination heats the nanoparticles on hundreds of femtoseconds timescales. The results resolve a multi-directional energy exchange on timescales shorter than the electronic thermalization of the nanometal. Electron-phonon coupling and diffusive charge-transfer determine the subsequent energy flow. This complex dynamics opens perspectives for optoelectronic and photocatalytic applications, while providing a constraining experimental testbed for state-of-the-art modelling.


Funder: Alexander von Humboldt‐Stiftung; Id:

Funder: National Sciences and Engineering Research Council of Canada


2D semiconductors, femtosecond electron diffraction, hybrid plasmonics, interfacial charge transfer, light-matter interactions

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Adv Mater

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HORIZON EUROPE European Research Council (ERC‐2015‐AdG‐694097, ERC‐2015‐CoG‐682843)
H2020 Future and Emerging Technologies (OPTOlogic 899794)
Deutsche Forschungsgemeinschaft (SFB 951, RE 3977/1, SFB/TRR 227, FOR 1700, SPP 2244)
H2020 Marie Skłodowska‐Curie Actions (101003436 ‐ PLASMMONS)
Narodowym Centrum Nauki (2019/35/B/ST5/00248)