Intertwined relaxation processes & athermal electron distributions in laser-excited solids
Prof. Dr. Bärbel Rethfeld
Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau
16:15 - 17:15 Tuesday 14 January 2025 TUG Femtosecond laser pulses irradiating a solid material induce a cascade of processes starting with the excitation of so-called hot electrons and passing through various relaxation processes. Several scattering mechanisms act on different timescales. At sufficiently high energy densities, phase transitions and ultrafast structural dynamics can be induced.
We simulate the dynamics of a large ensemble of excited electrons using complete Boltzmann collision integrals. We consider the excitation of conduction electrons in a metal or in a wide-band gap dielectric with visible light. On a femtosecond timescale, the electrons' energy distribution deviates strongly from a Fermi distribution.
During relaxation, electron-electron and electron-phonon scattering mutually influence each other. For materials with several electronic systems, e.g. itinerant ferromagnets or dielectrics, temperatures and densities equilibrate independently. I present results showing that athermal electron distributions as well as highly excited electrons can exist much longer than the single-electron lifetime predicts.
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