Regensburg 2025 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 7: Spins in Molecular Systems: Strategies and Effects of Hyperpolarization
DS 7.3: Vortrag
Mittwoch, 19. März 2025, 10:15–10:30, H14
The CISS magnetoresistance effect for polyalanine and polyproline molecules studied by ambient STM — •Thi Ngoc Ha Nguyen1, Lech Tomasz Baczewski2, Tobias Theiss3, Tanja Gulder3, and Christoph Tegenkamp1 — 1Solid Surface Analysis, Institute of Physics, Chemnitz University of Technology, Chemnitz, Ger- many — 2Reichenhainerstr., 70 — 3Institute of Organic Chemistry, Faculty of Chemistry and Mineralogy, Leipzig University, Leipzig, Germany
The chirality induced spin selectivity (CISS) effect has been up to now measured in a wide variety of systems but its exact mechanism is still under debate. Whether the spin polarization occurs at an interface layer or builds up in the helical molecule is yet not clear. We investigated the current transmission through helical polyalanine molecules, revealing a strong and length dependent dipole moment, as a part of a tunnel junction realized with a scanning tunneling microscope. Depending on whether the molecules were chemisorbed directly on the magnetic Au/Co/Au substrate or at the STM Au-tip, the magnetizations of the Co layer had been oriented in the opposite direction in order to preserve the symmetry of the IV-curves. These results show that besides the helicity also the electric dipole play a crucial role. Latest experiments with polyproline with a small electric dipole moment showed that the CISS effect is almost vanishing. Our results can be explained by a spin-polarized or spin-selective interface effect, induced and defined by the helicity and electric dipole orientation of the molecule at the interface.
Keywords: CISS MR; dipole moment; chiral; ambient STM