Role of Electrode Polarization in the Electron Transport Chirality-Induced Spin-Selectivity Effect

The electron transport manifestation of the chirality-induced spin-selectivity (CISS) effect is observed in metal-molecule-ferromagnet junctions, where the total current is different when the ferromagnet is magnetized parallel or antiparallel to the molecular chirality axis. Here, we discuss the relation between this appearance of the CISS effect and spin polarization of the ferromagnetic electrode. We show analytically that the experimental results indicate that the origin of the CISS effect must involve some interaction mechanism (as opposed to noninteracting electronic effects), since the observed CISS polarization can be much larger than the ferromagnetic electrode spin-polarization. Specifically, we show that a noninteracting single-level model cannot reproduce experimental data even if the molecular spin-filtering is perfect, and on the other hand, that the recently suggested spinterface mechanism for the CISS effect can indeed lead to arbitrarily large CISS polarization, with realistic physical parameters. We demonstrate this by showing an excellent fit between the spinterface model and recent experiments where the effective magnetization of the ferromagnetic electrode was changed continuously. We conclude that theoretical suggestions for the physical mechanism of the CISS which are based on noninteracting electrons can be ruled out.