Spin-Locked Helical Currents and Pure Spin Pumping in Altermagnetic Nanotubes

Abstract

Altermagnetism has been widely explored in 3D and 2D crystals, but its one-dimensional realization remains largely unexplored. Here we propose an altermagnetic nanotube formed by rolling a 2D altermagnet, which converts momentum-odd spin polarization into spin-chirality locking enforced by the screw axis. Unlike curvature-induced magnetization in bent films, the nanotube is mirror-antisymmetric and produce no net magnetization. Two reciprocal effects emerge: (i) a single-spin injection drives a helical current whose handedness is fixed by the spin, yielding opposite-sign axial magnetic fields; and (ii) a time-varying axial flux generates a circumferential Faraday field that drives equal-magnitude but opposite axial charge currents in the two spin channels, producing a pure spin current under open-circuit conditions. As an implication, spin accumulation programs the tube's handedness and can imprint it onto otherwise achiral coaxial nanotubes in one-dimensional van der Waals assemblies. First-principles results for V2Se2O confirm spin-dependent helical wave functions near both band edges, establishing a nonrelativistic route to spin-programmable chiral nanodevices and compact flux generators/charge-neutral spin injectors without static magnetic bias.