A symmetry analysis on Chirality Induced Spin Selectivity
J.W.J. van de Kamp (TU Delft - Electrical Engineering, Mathematics and Computer Science)
J.M. Thijssen – Mentor (TU Delft - Applied Sciences)
J.L.A. Dubbeldam – Mentor (TU Delft - Electrical Engineering, Mathematics and Computer Science)
M.T. Wimmer – Graduation committee member (TU Delft - QRD/Wimmer Group)
W.G.M. Groenevelt – Graduation committee member (TU Delft - Electrical Engineering, Mathematics and Computer Science)
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Abstract
Chirality Induced Spin Selectivity is the phenomenon where the chirality of certain molecules favours the transmission of electrons based on their spin. Among many examples, this long-studied phenomenon appears in two-terminal transport experiments, where different magnetisations of the leads can give different current-voltage characteristics. In previous research by Rikken [20], the chiral geometry of the device was determined as a necessary condition for antisymmetric IV curves.
In this thesis, we implemented a Büttiker probe (BP) in a 6-helicene model based on the previous work of Geyer [9]. The probe mimics the decoherence in a two-terminal CISS experiment. Moreover, this enables us to magnetise both leads independently. By altering the magnetisation of the leads and the orientation of the Büttiker probe, we were able to analyse many possible experimental setups. This enabled us to express the current difference in terms of bias voltage, magnetisation and BP orientation, where the latter was the research objective.
Isotropic Büttiker probes lead to a CISS effect, which is absent in a coherent electron transport model. Further research is needed to determine the exact nature of the numerical errors in our isotropic BP experiments. The results of anisotropic BPs can be explained assuming that the current difference is linear in the anisotropy of the BP. Further research is needed to strengthen this conjecture. These results are supported for lead magnetisation along an axis, perpendicular to the helical axis of the molecule, as well as magnetisation along this helical axis.