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Abstract
Ultrafast laser excitation drives metals into a highly non-equilibrium state, where the coupled dynamics of electrons, spins, and lattice degrees of freedom unfold on femtosecond to picosecond timescales. A microscopic understanding of these dynamics and the associated energy flow is essential for applications ranging from ultrafast spintronics and photocatalysis to laser material processing and inertial fusion energy.
This talk presents theoretical results for metals irradiated by ultrashort-pulse lasers, and compares them with experimentally accessible observables. The analysis spans a wide range of timescales, from the initial laser excitation to the final material modification.
We describe the temporal evolution of the non-thermal energy distribution of hot carriers in a kinetic framework based on full microscopic Boltzmann collision integrals. Including spin resolution in the description of itinerant ferromagnets, we find intrinsically energy-dependent spin dynamics that determine the magneto-optical response. We demonstrate that the effective electron-phonon coupling is strongly influenced by dynamically changing non-equilibrium electronic and phononic distributions, which can result in a collapse of the energy transfer rate. We compare molecular dynamics simulations of ultrafast melting with ultrafast electron diffraction measurements and further show how the structural dynamics feed back on the optical response of polycrystalline metals.
Bio
Baerbel Rethfeld is a Professor of Applied Theoretical Physics in Kaiserslautern, Germany. Her research focuses on the theoretical description of ultrafast dynamics in laser-excited solids over a broad range of excitation intensities, involving the interplay of coupled scattering processes across multiple timescales. She develops effective models to describe the response of materials under transient non-equilibrium conditions.
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