Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 42: Electron-driven Processes

O 42.5: Talk

Tuesday, March 18, 2025, 15:00–15:15, H11

Nonthermal phonon distributions induced by hot electrons — •Tobias Held, Christopher Seibel, Markus Uehlein, Sebastian T. Weber, and Baerbel Rethfeld — Department of Physics and Research Center OPTIMAS, RPTU Kaiserslautern-Landau

When an ultrashort laser pulse irradiates a metal, the electrons initially absorb the energy and rapidly establish a hot Fermi distribution. Subsequently, on a picosecond timescale, the electrons transfer energy to the phonon system. Electrons exhibit a stronger coupling to high-wavenumber phonons, leading to nonthermal phonon distributions induced by electron-phonon scattering.

In this study, we use the Boltzmann equation to examine the formation and subsequent relaxation of nonequilibrium phonon distributions. For our model system, we find that the majority of the energy is transferred within 10 ps, while a pronounced phonon nonequilibrium is induced. We observe "hot phonons" at the edge of the Brillouin zone, leading to a collapse of the electron-phonon energy transfer rate. Consequently, a finite temperature difference between electrons and phonons may persist significantly longer than the widely used two-temperature model would predict.

Keywords: electron-phonon; Boltzmann; hot phonons; nonequilibrium