Dresden 2026 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 26: Poster II

HL 26.54: Poster

Mittwoch, 11. März 2026, 09:30–11:30, P1

Ultrafast Lattice Dynamics in Gold Beyond the Kinematic Approximation — •Helena Hollstein^1,2, Sebastian Hammer², and Heinrich Schwoerer¹ — ¹Max-Planck-Institut für Struktur und Dynamik der Materie, 22761 Hamburg, Germany — ²Experimental Physics 6, University of Würzburg, 97074 Würzburg, Germany

In the interpretation of electron diffraction experiments, the kinematic scattering approximation and simple phonon models are often used to reduce computational cost when modeling structural dynamics [1]. However, even for well-studied benchmark systems such as polycrystalline gold thin films, it often remains unquestioned how reliably these assumptions hold under strong nonequilibrium excitation [2].

In this work, we investigate a 20 nm gold thin film under optical excitation using ultrafast electron diffraction (UED) and static temperature dependent electron diffraction to extract transient atomic displacements and determine phonon excitation by analyzing the Debye-Waller effect. We compare our experimental findings of lattice heating dynamics with simulated diffraction patterns that rely on kinematic scattering and harmonic phonon models. We hereby assess to what extent the commonly used theoretical frameworks cease to describe the structural response accurately. Our findings demonstrate that neglecting possible anharmonic potentials, phonon-phonon coupling and multiple scattering-effects can lead to systematic misinterpretations of ultrafast lattice dynamics and thermophysical material properties.
[1] Schäfer et al. Chem. Phys. Lett. 515 (2011)
[2] Durham et al. Struct. Dyn. 9 064302 (2022)

Keywords: structural dynamics; ultrafast electron diffraction; kinematic approximation; phonons; gold