REPLAY - SSE9 - Aurélien CRUT

The sudden absorption of energy by a metal nano-object launches a series of relaxation processes (internal thermalization, acoustic vibrations, cooling,…) involving femtosecond to nanosecond timescales, whose investigation allows to better understand how the macroscopic laws ruling electron interactions, elasticity, heat conduction or interfacial energy transfer are modified at the nanoscale. Optical pump-probe spectroscopy (based on the excitation of nano-objects by a femtosecond pump pulse, and the monitoring of their subsequent relaxation dynamics using another, time-delayed, probe pulse) constitutes a powerful experimental approach for such investigations. Moreover, the realization of such experiments on individual nano-objects and their analysis with multiphysics numerical simulations enable highly quantitative investigations of the ultrafast dynamics of metal nano-objects and of the transient changes of optical response that they induce.

Recent investigations on the vibrational and cooling dynamics of metal nano-objects were presented in this talk. These studies have in particular clarified the applicability of continuum mechanical models using bulk elastic constants to nanoparticles, and shown a promising approach to significantly improve the vibrational quality factors of supported nano-objects. They have also shed light on the dependence of the cooling dynamics of substrate-supported nano-objects on the morphological and thermal properties of the nano-objects and of their environment, and demonstrated that the sensitivity of time-resolved signals to transient heating largely depends on the probing wavelength.