  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.
