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TT: Fachverband Tiefe Temperaturen

TT 37: Ultrafast electron dynamics at surface and interfaces – Poster (joint session O/TT)

TT 37.6: Poster

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

Thermalization of optically excited electrons in metals: electron-electron scattering dynamics — •Stephanie Roden, Christopher Seibel, Tobias Held, Markus Uehlein, Sebastian T. Weber, and Baerbel Rethfeld — Department of Physics and Research Center OPTIMAS, RPTU University Kaiserslautern-Landau

When a metal is irradiated with a short-pulsed optical laser, the electron distribution is disturbed into a state far from equilibrium. On a femtosecond timescale, the non-thermal electrons thermalize by collisions with each other, which drives the electrons towards a hot Fermi distribution.

In this work, we present a derivation of the full electron-electron Boltzmann collision integral within the random-k approximation. Building on this approach, we trace the temporal evolution of the electron energy distribution in metals after ultrafast excitation. Furthermore, we examine to which extent the resulting dynamics can be captured by the numerically simpler relaxation time approach, applying a constant and an energy-dependent relaxation time derived from Fermi-liquid theory.

We find a better agreement with the latter, while specific features caused by the balance of scattering and reoccupation can only be captured with a full collision integral.

Keywords: Electron energy distribution functions; Electron scattering; Ultrashort laser excitation; Boltzmann collision integral; Relaxation time approach