Synergy and Competition of Dual Chirality in the Chirality-Induced Spin Selectivity of Supramolecular Helices.

The construction of supramolecular assemblies with hierarchical chirality provides a new platform for exploring the chirality-induced spin selectivity (CISS) effect. In this work, we systematically investigate CISS in multichiral systems using a class of multilayer helical architectures. Each layer consists of stacked helical rings with well-defined local chirality. By introducing controlled interlayer twisting, a global helical handedness is imposed, forming tubular multichiral helices. Including geometric spin-orbit coupling and dephasing in our theoretical model, we find that the interplay of local and global chirality leads to enhanced magnetoresistance (MR) and the simultaneous appearance of transverse and longitudinal CISS signals. We also examine two common approaches for including dephasing. Self-consistent Büttiker voltage probes preserve charge current conservation in the two-terminal subspace and yield zero linear MR. Leakage dephasing produces finite linear MR but only by breaking two-terminal current conservation. Neither method alone provides a fully self-consistent explanation for two-terminal linear CISS MR. More generally, when the self-energy satisfies a generalized time-reversal condition, global Onsager reciprocity is maintained. Beyond this condition, a genuine linear MR requires a reciprocity-breaking mechanism that is both charge-conserving and linked to molecular chirality. The dual-chiral geometry breaks the symmetry of single helices and induces an anomalous angular phase shift in MR. In addition, Floquet analysis shows that the interplay between local and global chirality enables controlled switching of spin polarization under circularly polarized light. These results establish a fundamental framework for understanding CISS in multichiral superstructures and provide design principles for integrated spin, optical, and magnetic control in multichiral spintronic devices.