Regensburg 2022 – scientific programme
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O: Fachverband Oberflächenphysik
O 37: Plasmonics and Nanooptics 1
O 37.4: Talk
Wednesday, September 7, 2022, 11:30–11:45, H3
Theory of radial oscillations in metal nanoparticles driven by optically induced electron density gradients — •Robert Salzwedel1, Andreas Knorr1, Dominik Höing2,3, Holger Lange2,3, and Malte Selig1 — 1Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, 10623 Berlin, Germany — 2Institut für Physikalische Chemie, Universität Hamburg, 20146 Hamburg, Germany — 3The Hamburg Centre for Ultrafast Imaging, 22761 Hamburg, Germany
Upon optical excitation, metal nanoparticles oscillate in radial breathing modes. These oscillations are assumed to be driven mainly by the thermalization of hot electrons impulsively heating the lattice, which can be described classically [1,2]. Based on a combined approach of quantum hydrodynamics and Heisenberg equations of motion for the optical excitation of electron gas in metal nanoparticles and the associated electron-phonon interaction, we discuss the contribution of additional coherent sources to the radial breathing oscillations.
Our results reveal a more direct coupling mechanism between the field and phonons compared to the established interpretation of experiments: the optical pulse induces spatial gradients in the electron density that drive phonon oscillations coherently and directly on the time scale of the optical excitation. Therefore, thermal and coherent contributions must be considered in the early times of the oscillation.
[1] Hartland, G. V. et al., JCP, 116, 8048 (2002)
[2] Hodak, J. H. et al., JCP, 111, 8613 (1999)