Berlin 2024 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Poster: Ultrafast Electron Dynamics at Surfaces and Interfaces

O 36.2: Poster

Dienstag, 19. März 2024, 18:00–20:00, Poster C

Second harmonic spectroscopy of Fe-porphyrin/Cu(001) interfaces — •Newsha Vesalimahmoud, Mahendra Kabbinahithlu, Ping Zhou, Uwe Bovensiepen, and Andrea Eschenlohr — University of Duisburg-Essen, Faculty of Physics and CENIDE, Lotharstr. 1, 47057 Duisburg, Germany

Hybrid systems of metallo-porphyrin/metal interfaces, which are known as spinterfaces, are promising candidates to control the spin-dependent transport in spintronic devices [1]. This study focuses on the iron porphyrin molecules (FeOEP)/Cu(001) interface using interface-sensitive time-resolved second harmonic generation (SHG) spectroscopy. We analyze the polarization and wavelength dependent SHG for different molecular adsorbate thicknesses on Cu(001) using a fundamental beam in the range of 500 - 700 nm. Polarization dependent measurements show a higher p-P SHG yield than s-P SHG, as the intrinsic absolute value of χ_zzz⁽²⁾ is much larger than χ_zxx⁽²⁾ . Moreover, SHG spectra show an increasing intensity up to a maximum at 2.3 eV for Cu(001) due to one ω resonance. After adsorption of 2 monolayers (ML) and 5ML FeOEP/Cu(001), the spectral dependence remains similar to the Cu(001) surface except for an enhancement at 2.25 eV for 5ML FeOEP/Cu(001). We attribute this enhancement to the energetic position of the lowest unoccupied molecular orbital (LUMO) at the FeOEP/Cu(001) interface. Moreover, we discuss the electron dynamics analyzed through pump-probe SHG at on- and off-resonant photon energies.

[1] Wende, H., et al., Nat. Mater, 6, 516 (2007).

Keywords: second harmonic spectroscopy; molecule/metal interface; porphyrin molecules; non-linear optics; electron dynamics