Spin-Locked Helical Currents and Charge-Neutral Spin-Channel 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 \textcolor{black}{symmetry-enforced directional spin anisotropy in momentum space} into \textcolor{black}{spin--chirality locking in the screw-symmetric geometry}. Unlike curvature-induced magnetization in bent films, \textcolor{black}{the nanotube remains compensated and produces no net magnetization}. Two reciprocal effects emerge: (i) \textcolor{black}{spin-selective} 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 \textcolor{black}{equal and opposite axial charge currents in the two fixed spin channels, yielding a charge-neutral spin-channel current in the open-circuit weak-SOC limit}. \textcolor{black}{Explicit the first-principles calculations of the relaxed V${}_2$Se${}_2$O nanotube reveal spin-resolved helical $|\ddot{I}ˆ{|}^2$ modulations near both band edges, while a parent-monolayer Wannier--Boltzmann calculation quantifies the energy-dependent spin-odd transverse response and corresponding ideal thin-wall field scale.