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arXiv · 2609.26722

The Role of Electron Correlations in Chirality Induced Spin Selectivity of Molecular Junctions

A. Konidena·J. Fransson·L. Kantorovich
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Abstract

The Non-Equilibrium Green's Function (NEGF) approach is applied to a chain of Hubbard atoms in a helical geometry sandwiched between two leads, one of which is magnetic, to assess what role the electronic correlation effects within the molecule may play in explaining the Chirality Induced Spin Selectivity (CISS) effect. The correlation effects are treated at the level of the self-consistent second Born approximation. Two chiralities, Laevorotatory (L) and Dextrorotatory (D), of the helix, are discussed. Further, we account for spin-orbit coupling (SOC) within the chains using a simplified model of Kane and Mele that exploits next-nearest neighbour interactions intrinsic to a curved geometry. The interaction with the leads is considered within the Wide Band Approximation. We consider the ratio, U/t, of the Hubbard constant U to the hopping t between atomic sites along the chain of up to two, but found very little spin polarisation in our calculations. Even though the spin polarisation factor defined as a relative difference between the largest and smallest total current is found for both enantiomers practically the same, the orientation of the tip's polarisation required to reach the largest and smallest currents for the two enantiomers differed. It is also found that the qualitative agreement with observations can only be achieved if we account, self-consistently, for the second order of the perturbation theory. The distribution of the spin populations on the chain atoms for different U/t ratios is also discussed. This study concludes that even though accounting for electron-electron interactions are important in understanding spin selectivity within molecular junctions, they cannot be made solely responsible for the high spin polarisation factors observed in experiments.

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A. Konidena, J. Fransson, L. Kantorovich. 2026-09-22. The Role of Electron Correlations in Chirality Induced Spin Selectivity of Molecular Junctions. https://arxiv.org/abs/2609.26722

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