Femtosecond Nonequilibrium Electronic Heat Transport in Thin Gold Films

Abstract

With the advent of femtosecond lasers has come the promise of directly measuring ultrafast electron transport effects in technologically important materials. Using a front pump/back probe1 measurement of transient reflectivity changes, we have observed ultrafast electronic heat transport through thin films of gold. For film thicknesses of 500 - 2000 Å, we find thermal transport occurs on a time scale of 40 - 200 fs. In this regime, the transport of heat seems to be governed by electronic motion, since lattice heat diffusion times are much slower.