Exact theory of chirality-dependent p-wave magnetism and Edelstein effect in spin spirals

Abstract

Spin-momentum locking is widely regarded as a hallmark of relativistic spin-orbit coupling. Here we demonstrate analytically that it can instead emerge solely from magnetic chirality. Solving the minimal tight-binding model of electrons coupled to a spin spiral using a generalized Bloch theorem, we show that the spiral generates chirality-dependent p-wave magnetism characterized by the antisymmetric spin texture $\mathbf{s}(\mathbf{k})=-\mathbf{s}(-\mathbf{k})$. The exact solution further yields closed-form expressions for the electrical conductivity and the spin Edelstein susceptibility, revealing a microscopic mechanism by which magnetic chirality alone can generate spin polarization without spin-orbit coupling, with direct implications also for chirality-induced spin selectivity. In the strong exchange-coupling regime, the spin-dependent physics of the spin spiral becomes directly analogous to the orbital-dependent physics of electrons propagating through a non-magnetic helix. Our work establishes a minimal exactly solvable model of chirality-induced spin-momentum locking and spin-charge conversion beyond the conventional spin-orbit coupled paradigm.

6 pages, 4 figures. This work was supported by the EIC Pathfinder OPEN grant 101129641 "Orbital Engineering for Innovative Electronics" and by Deutsche Forschungsgemeinschaft (DFG): Project No. 328545488 - CRC/TRR 227, Project No. B12 and by the German Excellence Strategy -EXC3112/1 -533767171 (Center for Chiral Electronics)