Ultrafast laser irradiation of metals: Beyond the two-temperature model

The well-known two-temperature model is a valuable tool to investigate ultrafast electron dynamics, despite its inadequacy to describe the initial nonthermal carrier distribution. Based on simple assumptions, an extension of the model is proposed, which overcomes this limitation, incorporating the transient electronic excitation process induced by an ultrafast laser pulse and the subsequent relaxation via electron-electron and electron-phonon scattering. The most interesting features of the extended model, such as its ability to investigate the dependence of the sample thermal response on the photon energy and to identify distinct heating terms for the electronic and the lattice temperatures, are illustrated with the help of some explanatory simulations.