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Energy and Momentum Distribution of Surface Plasmon-Induced Hot Carriers Isolated via Spatiotemporal Separation.

Authors
  • Hartelt, Michael1
  • Terekhin, Pavel N1
  • Eul, Tobias1
  • Mahro, Anna-Katharina1
  • Frisch, Benjamin1
  • Prinz, Eva1
  • Rethfeld, Baerbel1
  • Stadtmüller, Benjamin1, 2
  • Aeschlimann, Martin1
  • 1 Department of Physics and Research Center OPTIMAS,TU Kaiserslautern, Erwin-Schrödinger-Straße 46, 67663 Kaiserslautern, Germany. , (Germany)
  • 2 Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany. , (Germany)
Type
Published Article
Journal
ACS Nano
Publisher
American Chemical Society
Publication Date
Dec 01, 2021
Identifiers
DOI: 10.1021/acsnano.1c06586
PMID: 34852458
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

Understanding the differences between photon-induced and plasmon-induced hot electrons is essential for the construction of devices for plasmonic energy conversion. The mechanism of the plasmonic enhancement in photochemistry, photocatalysis, and light-harvesting and especially the role of hot carriers is still heavily discussed. The question remains, if plasmon-induced and photon-induced hot carriers are fundamentally different or if plasmonic enhancement is only an effect of field concentration producing these carriers in greater numbers. For the bulk plasmon resonance, a fundamental difference is known, yet for the technologically important surface plasmons, this is far from being settled. The direct imaging of surface plasmon-induced hot carriers could provide essential insight, but the separation of the influence of driving laser, field-enhancement, and fundamental plasmon decay has proven to be difficult. Here, we present an approach using a two-color femtosecond pump-probe scheme in time-resolved 2-photon-photoemission (tr-2PPE), supported by a theoretical analysis of the light and plasmon energy flow. We separate the energy and momentum distribution of the plasmon-induced hot electrons from that of photoexcited electrons by following the spatial evolution of photoemitted electrons with energy-resolved photoemission electron microscopy (PEEM) and momentum microscopy during the propagation of a surface plasmon polariton (SPP) pulse along a gold surface. With this scheme, we realize a direct experimental access to plasmon-induced hot electrons. We find a plasmonic enhancement toward high excitation energies and small in-plane momenta, which suggests a fundamentally different mechanism of hot electron generation, as previously unknown for surface plasmons.

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