Cooling Dynamics of a Gold Nanoparticle in a Host Medium Under Ultrafast Laser Pulse Excitation: A Ballistic-Diffusive Approach

TL;DR

This paper develops a numerical model to analyze the ultrafast cooling dynamics of a gold nanoparticle in a host medium, revealing slower heat transfer and higher temperature rise than traditional Fourier-based predictions.

Contribution

It introduces a ballistic-diffusive heat conduction model for nanoparticle cooling, capturing nonlocal and nonequilibrium effects absent in classical Fourier law approaches.

Findings

Heat transfer from nanoparticle to medium is slower than Fourier law predicts.

Nanoparticle temperature rise is significantly higher during ultrafast excitation.

Cooling dynamics are markedly slower due to nonlocal heat conduction effects.

Abstract

We present a numerical model allowing to determine the electron and lattice temperature dynamics in a gold nanoparticle under subpicosecond pulsed excitation, as well as that of the surrounding medium. For this, we have used the electron-phonon coupling equation in the particle with a source term linked with the laser pulse, and the ballistic-diffusive equations for heat conduction in the host medium. Our results show that the heat transfer rate from the particle to the matrix is significantly smaller than the prediction of Fourier's law. Consequently, the particle temperature rise is much larger and its cooling dynamics is much slower than that obtained using Fourier's law, which is attributed to the nonlocal and nonequilibrium heat conduction in the vicinity of the nanoparticle. These results are expected to be of great importance for interpreting pump-probe experiments performed on single nanoparticles or nanocomposite media.