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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 32: Focus Session: Novel Approaches to Surface Plasmon Generated Charges and Heat for Photocatalysis I (joint session O/CPP)
CPP 32.3: Talk
Wednesday, March 20, 2024, 15:45–16:00, MA 141
Superlattice excitation driven by electron-phonon interaction measured with UXRD — •Jan-Etienne Pudell1, Marc Herzog2, Max Mattern2, Alexander von Reppert2, Daniel Schick3, Ulrike Boesenberg1, Angel Rodriguez-Fernandez1, Wonhyuk Jo1, Roman Shayduk1, Wei Lu1, Gregory Malinowski5, Michel Hehn5, Matias Bargheer2,4, and Anders Madsen1 — 1European XFEL, Germany — 2Institut für Physik, Uni Potsdam, Germany — 3MBI, Berlin — 4HZB Berlin, Germany — 5IJL, Université Lorraine, France
The transport of heat (or energy in general) in nanoscopic heterostructures is of great fundamental as well as technological interest, e.g. in the context of thermal management in devices, heat-assisted magnetic recording or plasmonic catalysis. In metal heterostructures, heat conduction is usually dominated by electrons which can be at strong non-equilibrium with lattice vibrations on ultrashort time scales. Utilizing ultrafast x-ray diffraction (UXRD) at the MID end-station at European XFEL, we investigate the ultrafast structural response of a laser-excited metal-metal superlattice (SL) consisting of few-nm thick metal layers with low (Cu) and high (Pt) electron-phonon coupling on top of a 100 nm Cu and 20 nm Ni layer. Using the transient shift and intensity modulations of the respective Bragg peaks, we can quantify the ultrafast heat flow in the SL by comparison to a time-dependent diffusive two-temperature transport model. We identify the excitation of the SL phonon mode as well as an efficient heat transport from the laser excited SL to the Ni-layer via hot electrons.
Keywords: ultrafast x-ray diffraction; nanoscale heat transfer; electron-phonon coupling; Free electron laser