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Chirality-induced spin selectivity (CISS), in which electrons transmitted through nonmagnetic chiral materials exhibit strong spin-dependent transport, has attracted growing interest for spintronic applications [1]. Experiments have reported spin polarizations of several tens of percent in a variety of quasi-one-dimensional chiral systems, including DNA, oligopeptides, helicenes, and helical molecular aggregates. Although theoretical mechanisms based on intraband spin–orbit coupling (SOC) and on-site Coulomb interactions have been proposed [2,3], a quantitative understanding of CISS remains elusive, partly because most previous studies rely on single-band models.
In this work, we theoretically investigate multiband effects on the magnetoresistive response associated with CISS. We adopt a two-site, two-band extended Hubbard model as a minimal model for chiral molecular aggregates, incorporating interband SOC, on-site Coulomb interactions, and electron hopping. The nonequilibrium steady-state current is evaluated using the Gorini–Kossakowski–Lindblad–Sudarshan (GKLS) master equation.
We show that the magnetoresistive effect vanishes in the absence of electron correlations, whereas finite Coulomb interactions induce a sizable spin polarization that is enhanced with increasing interaction strength. Notably, spin polarization exceeding 25% is achieved even when the SOC strength is much smaller than the electron hopping amplitude. These results demonstrate the essential role of interband SOC in multiband CISS mechanisms.
[1] D. H. Waldeck, R. Naaman, and J. Subotnik, Physics Today (2026).
[2] J. Fransson, J. Phys. Chem. Lett. 10, 7126 (2019).
[3] K. H. Huisman et al., J. Phys. Chem. C 127, 6900 (2023).