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O: Fachverband Oberflächenphysik

O 40: Ultrafast electron dynamics at surface and interfaces – Poster (joint session O/TT)

O 40.1: Poster

Dienstag, 10. März 2026, 14:00–16:00, P2

Nonequilibrium phonon dynamics after laser-excitation — Tobias Held, Christopher Seibel, Markus Uehlein, •Sebastian T. Weber, and Baerbel Rethfeld — Department of Physics and Research Center OPTIMAS, RPTU University Kaiserslautern-Landau

Electron-phonon coupling is a fundamental process governing the energy relaxation dynamics of solids excited by ultrafast laser pulses. While this coupling is often described in terms of an effective electron temperature, recent works have highlighted the important roles of both nonequilibrium electronic distributions and detailed phononic properties.

In this study, we investigate how nonequilibrium electron occupations, phonon stiffness, and wavenumber-resolved coupling collectively shape the energy exchange between electrons and the lattice in metals. We find that deviations from thermal electronic distributions can substantially modify the coupling parameter, challenging the conventional assumption that electron temperature alone determines the coupling strength. We further identify a roughly quadratic scaling of the coupling parameter with phonon stiffness, with high-wavenumber phonon modes consistently dominating the interaction. Finally, we demonstrate that this preferential coupling leads to the emergence of hot phonons near the Brillouin-zone boundary, which in turn induces a collapse of the overall energy transfer rate and significantly delays electron-phonon equilibration.

Keywords: Electron-Phonon Coupling; Non-equilibrium; Boltzmann Equation