title: Proper definition of spin current in spin-orbit coupled systems.
abstract: The 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.
authors.affiliation: Institute of Physics and ICQS, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
authors.forename: Junren
authors.initials: J
authors.lastname: Shi
authors.forename: Ping
authors.initials: P
authors.lastname: Zhang
authors.forename: Di
authors.initials: D
authors.lastname: Xiao
authors.forename: Qian
authors.initials: Q
authors.lastname: Niu