Acoustic vibrations of metal nano-objects: Time-domain investigations

Tailored Hypersound Generation in Single Plasmonic Nanoantennas

“…Indeed, modeling based on the solution of Navier's equation of continuum mechanics shows excellent agreement with experimental results, diverging from atomistic method predictions only for objects comprising a few hundreds of atoms [23,26]. Although nanomaterials are widely studied due to unique properties arising at this size regime, the invariance of some of the physical properties of nanosized materials compared to their bulk counterparts, for instance the Young's modulus for gold nanowires [27], justifies a macroscopic approach when applied to such a small size regime [23].…”

“…Those oscillations, known as coherent acoustic phonons, produce periodic perturbations in the dielectric constant which can be detected as a transmission change of a probe pulse. For frequency modes on the order of few tens of picoseconds, the main excitation mechanism comes from the lattice dilation produced by the fast heating of the lattice with a concomitant change in the oscillator equilibrium position [23].…”

“…Finite element methods for linear elastic theory have been established as a powerful tool to validate and predict the acoustic response of objects extending from a few nanometers in size to those of macroscopic dimensions [23]. Indeed, modeling based on the solution of Navier's equation of continuum mechanics shows excellent agreement with experimental results, diverging from atomistic method predictions only for objects comprising a few hundreds of atoms [23,26].…”

“…F(t) is the driving force which is defined by the specific light-matter interaction. It is well known [19,23] that for metal nanostructures the driving force has two main contributions, one from the electron and the other from the lattice heating.…”

Backward propagating acoustic waves in single gold nanobeams

“…While backward wave propagation in elastic waveguides has been predicted and already observed at the macroscale, very few studies have been done at the nanoscale. Here, we show that these backward waves can be used as the unique signature of the width dilatational acoustic mode.Probing the elasticity at the nanoscale is a challenge that led a wide community to study confined acoustic modes of nano-objects in the 10 GHz-1 THz range using time-resolved pump-probe experiments [1]. In such an approach, acoustic modes are excited by the absorption of a femtosecond laser pulse and detected in transmission [2,3] or reflectivity geometry in near [4,5] or far [6,7] field by the induced change in the material optical properties.…”