Observation of Multi‐Directional Energy Transfer in a Hybrid Plasmonic–Excitonic Nanostructure

Abstract

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.

Understanding the Photothermal and Photocatalytic Mechanism of Polydopamine Coated Gold Nanorods

“…Similar conclusions related to the acceleration of hot electron decay have been presented before for other interfacial systems coupled to Au. [62][63][64] The results support our hypothesis and suggest that electrons generated in Au, are quickly transferred to PDA, where they are available for reactions leading to the photodegradation observed in our experiment.…”

Reinforcing the Efficiency of Photothermal Catalytic CO2 Methanation through Integration of Ru Nanoparticles with Photothermal MnCo2O4 Nanosheets

“…Apart from the LSPR effect of metal nanoparticles, semiconductors with narrow bandgaps and intrinsic thermalization performance could also be excited to realize localized heating due to nonradiative recombination of the excitons, thus serving as “heating substrate” for the active metal nanoparticles, resulting in accelerated catalytic reaction kinetics . Furthermore, the formation of heterojunctions between plasmonic metal nanoparticles and photothermal semiconductors would potentially enhance charge carrier separation and reactant activation .…”

Dipolar Coupling at Interfaces of Ultrathin Semiconductors, Semimetals, Plasmonic Nanoparticles, and Molecules

“…To connect the exciton localization to related optical experiments that observe strong exciton-plasmon coupling, [41,[102][103][104][105] transmission T, reflection R, and true absorption A of TMDC-PC hybrids can be evaluated for a 2D PC, see Figure 5a, specified for the case of perpendicular incident plane-wave excitation…”

“…To connect the exciton localization to related optical experiments that observe strong exciton–plasmon coupling, [ 41,102–105 ] transmission T , reflection R , and true absorption A of TMDC–PC hybrids can be evaluated for a 2D PC, see Figure 5a, specified for the case of perpendicular incident plane‐wave excitation . In the course of this, an extension of the quasi‐static approximation is incorporated.…”