Berlin 2024 – scientific programme

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O: Fachverband Oberflächenphysik

O 48: Focus Session: Spin Phenomena in Chiral Molecular Systems II (joint session O/TT)

O 48.3: Talk

Wednesday, March 20, 2024, 11:30–11:45, MA 141

Spin polarization through a helical molecule- functinalized tip dependence on the tip-sample distance observed by ambient STM — •Thi Ngoc Ha Nguyen¹, Lech Tomasz Baczewski², Olav Hellwig³, and Christoph Tegenkamp¹ — ¹Analysis of Solid Surfaces, Nanostructures and Quantum Materials, Chemnitz University of Technology, Germany — ²Institute of Physics, Polish Academy of Sciences, Warszawa, Poland — ³Functional Magnetic Materials, Chemnitz University of Technology, Chemnitz, Germany

Polyalanine (PA) with an alpha-helix conformation has gathered recently a lot of interest as the propagation of electrons along the helical backbone structure comes along with spin polarization of the transmitted electron. However, studies on a molecular scale are still rare, although this length scale provides direct insight into the role of molecular properties. We studied now in detail with a PA molecule-functionalized Au tip on magnetic Au/Co/Au/Pt/Al2O3 substrates and probed the transmission by local spectroscopy (STS). Because of the high spatial resolution, our setup allows to study this CISS effect on the nanoscale and probe the importance of cooperative effects. Using this functionalized tip, we found that the spin polarization (SP) significantly varies with tip-sample distance. Interestingly, the SP through the self-assembled film of PA on the same substrate at different non-functionalized Au tip-sample distance doesn't show significant change. Our observation provides that the overlaping tip and sample orbitals, the coupling as well as the electric field strength in the close proximity of tip - sample surface take the main roles on this SP variation.

Keywords: Polyalanine; CISS; STM; Spinpolarization; Tip functionalization