Ultrafast laser irradiation of metals can often be described theoretically with the two-temperature model. The energy exchange between the excited electronic system and the atomic one is governed by the electron-phonon coupling parameter. The electron-phonon coupling depends on both, the electronic and the atomic temperature. We analyze the effect of the dependence of the electron-phonon coupling parameter on the atomic temperature in ruthenium, gold, and palladium. It is shown that the dependence on the atomic temperature induces nonlinear behavior, in which a higher initial electronic temperature leads to faster electron-phonon equilibration. Analysis of the experimental measurements of the transient thermoreflectance of the laser-irradiated ruthenium thin film allows us to draw some, albeit indirect, conclusions about the limits of the applicability of the different coupling parametrizations.

Light-Matter Interaction

Akhmetov, F., Medvedev, N., Makhotkin, I., Ackermann, M., & Milov, I. (2022). Effect of Atomic-Temperature Dependence of the Electron–Phonon Coupling in Two-Temperature Model. Materials, 15(15), 5193: 1–12. doi:10.3390/ma15155193