Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 98: Ultrafast electron dynamics at surface and interfaces IV
O 98.4: Talk
Friday, March 13, 2026, 10:30–10:45, TRE/MATH
Ultrafast energy flow among electrons and phonons in a Pb/Si nanoscale heterosystem — •Christian Brand1, Mohammad Tajik1, Tobias Witte1, Laurenz Rettig2, Birk Finke1, Björn Sothmann1, Uwe Bovensiepen1, and Michael Horn-von Hoegen1 — 1Department of Physics, University of Duisburg-Essen, Germany — 2Department of Physical Chemistry, Fritz Haber Institute, Germany
Microscopic excitations in condensed matter interact on ultrafast time scales. In this study, we employed time-resolved photoelectron spectroscopy and ultrafast electron diffraction to probe the spatially confined dynamics of electrons and phonons in ultrathin epitaxial Pb films on Si(111) subsequent to fs-laser excitation. Spatial confinement is crucial here, as without it, the energy flow into the unexcited bulk would obscure the transient dynamics and prevent targeted investigation. Electrons dissipate their excess energy within 400 fs, while lattice vibrations gradually build up over 3-8 ps. During this time gap, energy is transiently stored in high-frequency phonon modes, as captured by a three-temperature model. The transient electron temperature provides direct experimental access to the occupation of these phonons after equilibration at ≈ 3 ps. Subsequent excitation of low-frequency phonons and full lattice thermalization at ≈ 20 ps are governed by anharmonic phonon-phonon coupling within the Pb film.
Keywords: ultrafast dynamics; electron dynamics; lattice dynamics; ultrathin films; energy flow