2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/100447The conventional definition of spin current is incomplete and unphysical in describing spin transport in systems with spin-orbit coupling. A proper and measurable spin current is established in this study, which fits well into the standard framework of near-equilibrium transport theory and has the desirable property to vanish in insulators with localized orbitals. Experimental implications of our theory are discussed.Final version with updated journal-refMesoscale and Nanoscale Physicstext