Regensburg 2025 – scientific programme
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O: Fachverband Oberflächenphysik
O 30: Surface Magnetism
O 30.5: Invited Talk
Tuesday, March 18, 2025, 11:30–12:00, H11
Resonant molecular transitions in femtosecond second harmonic generation spectroscopy of Fe-porphyrin/Cu(001) — •Andrea Eschenlohr1, Rui Shi2, Jinghao Chen1, Ping Zhou1, Uwe Bovensiepen1, Wolfgang Hübner2, and Georg Lefkidis2 — 1Faculty of Physics and CENIDE, University Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany — 2Department of Physics, RPTU, Box 3049, 67653 Kaiserslautern, Germany
Metal-organic molecular adsorbates on metallic surfaces are potential future materials for (spin-)electronics applications, provided that the molecule-substrate interaction can be analyzed and manipulated in a targeted manner. By combining interface-sensitive optical second harmonic generation (SHG) spectroscopy experiments and electronic structure calculations using coupled cluster methods including optical excitations on iron-octaethylporphyrin (FeOEP) adsorbed on Cu(001), we find that the SHG response of FeOEP/Cu(001) is modified at 2.15-2.35 eV fundamental photon energy compared to the bare Cu(001) surface. We conclude a resonantly enhanced SHG by molecular transitions, which results from a strong charge-transfer character of the molecule-substrate interaction [1]. Pump-probe SHG reveals a markedly slower relaxation time at this resonance, indicating an increased lifetime of the optically induced state compared to the bare Cu(001) surface, which will be discussed in the context of charge transfer dynamics.
[1] Eschenlohr et al., arXiv:2409.09801
Keywords: porphyrins; molecule metal interfaces; second harmonic generation; ultrafast dynamics