Nguyen Thi Ngoc Ha, Salvan Georgeta, Hellwig Olav, Paltiel Yossi, Baczewski Lech Thomasz, Tegenkamp Christoph
Solid Surface Analysis, Institute of Physics, Chemnitz University of Technology 09126 Chemnitz Germany
Semiconductor Physics, Institute of Physics, Chemnitz University of Technology 09126 Chemnitz Germany.
Chem Sci. 2024 Aug 16;15(36):14905-12. doi: 10.1039/d4sc04435e.
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. Here we have investigated the current transmission through helical polyalanine molecules 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 -curves. This is the first time that the CISS effect is demonstrated for a tunneling junction without a direct interface between the helical molecules and the magnetic substrate. 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. In this sense, the helical molecule does not act as a simple spin-filter or spin-polarizer and the CISS effect is not limited to spinterfaces.
到目前为止，手性诱导自旋选择性（CISS）效应已在多种系统中得到测量，但其确切机制仍存在争议。自旋极化是发生在界面层还是在螺旋分子中形成尚不清楚。在这里，我们研究了通过螺旋聚丙氨酸分子的电流传输，该分子是用扫描隧道显微镜实现的隧道结的一部分。根据分子是直接化学吸附在磁性Au/Co/Au衬底上还是在STM Au尖端上，Co层的磁化方向相反，以保持I - V曲线的对称性。这是首次在螺旋分子与磁性衬底之间没有直接界面的隧道结中证明CISS效应。我们的结果可以用由分子在界面处的螺旋度和电偶极取向诱导和定义的自旋极化或自旋选择性界面效应来解释。从这个意义上说，螺旋分子并不充当简单的自旋过滤器或自旋极化器，并且CISS效应不限于自旋界面。
