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O: Fachverband Oberflächenphysik

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

O 40.2: Poster

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

Comparing temperature change during light-matter interaction of thermal and athermal electron systems — •Fabio A. Müller, Tobias Held, Christopher Seibel, Sebastian T. Weber, and Baerbel Rethfeld — Department of Physics and Research Center OPTIMAS, RPTU University Kaiserslautern-Landau

When an ultrashort laser pulse irradiates a metal, the electronic system initially absorbs energy and is driven far from equilibrium. This transient nonequilibrium distribution modifies the light-matter interaction, in part through changes in Pauli blocking, while electron-electron scattering concurrently drives the system toward a hot Fermi-Dirac distribution. Consequently, ultrashort laser pulses of the same fluence but different duration lead to different absorption, even in the linear regime.

Here, we investigate how the capability of an electron ensemble to absorb photons depends on its instantaneous energy distribution. Specifically, we compare the absorption arising from nonequilibrium electron distributions with that of Fermi-Dirac distributions carrying the same energy density. Our results show that, for realistic materials, the relative absorption is highly sensitive to the photon energy, a behavior that can be traced back to distinct features in the electronic density of states.

Keywords: nonequilibrium electrons; light-matter interaction; photon energy dependence