Ultrafast electron-lattice thermalization in copper and other noble metal nanoparticles

Denis Mongin (1) , Paolo Maioli (2) , Julien Burgin (3) , Pierre Langot (3) , Emmanuel Cottancin (4) , Sergio D’addato (5) , Bruno Canut (6) , Mona Tréguer-Delapierre (7) , Aurélien Crut (2) , Fabrice Vallée (2) , Natalia del Fatti (2)

1 ILM - Institut Lumière Matière [Villeurbanne]
2 iLM - FemtoNanoOptics - iLM - FemtoNanoOptics
3 LOMA - Laboratoire Ondes et Matière d'Aquitaine
4 iLM - AGNANO - iLM - Agrégats et nanostructures
5 UNIMORE - Università degli Studi di Modena e Reggio Emilia = University of Modena and Reggio Emilia
6 INL - S&N - INL - Spectroscopies et Nanomatériaux
7 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

Using time-resolved ultrafast pump-probe spectroscopy we investigated the electron-lattice energy transfer in small copper nanospheres with diameters ranging from 3.2 to 23 nm, either embedded in a glass or dispersed in a solvent. Electron-lattice scattering rate is shown to increase with size reduction, in agreement with our previous results obtained on gold and silver nanoparticles in the low excitation regime. We attribute this effect to the reduction of the screening efficiency of electron–phonon interactions close to the nanoparticle surface. To understand the discrepancy between the results on the electron-lattice scattering in different metals reported in the literature (reduction, no dependence or increase with nanoparticle size), we discuss the experimental conditions required for the accurate determination of electron-lattice energy transfer time from time-resolved investigations in the weak and strong excitation regimes and present power-dependent experiments on gold nanospheres in solution. Our findings are derived from a theoretical analysis based on the two-temperature model predictions and on a complete modeling of the nanoparticle transient extinction cross-section through the resolution of Boltzmann equation in the presence of hot electrons.

Mots clés: electron-lattice interactions; two-temperature model; ultrafast electron dynamics; pump-probe spectroscopy; copper nanoparticles

Domaines: Matériaux; Optique / photonique

Denis Mongin, Paolo Maioli, Julien Burgin, Pierre Langot, Emmanuel Cottancin, et al.. Ultrafast electron-lattice thermalization in copper and other noble metal nanoparticles. Journal of Physics: Condensed Matter, 2019, 31 (8), pp.084001 (1-11). ⟨10.1088/1361-648X/aaf7eb⟩. ⟨hal-01987430⟩