Current in a Spin-orbit-coupling System
  The formulae of particle current as well as spin- and angular momentum currents are studied for most spin-orbit coupling (SOC) systems. It is shown that the conventional expression of currents in some literatures are not complete for some SOC systems. The particle current in Dresselhaus system must have extra terms in additional to the conventional one, but no extra term for Rashba, Luttinger model. Further more, we also prove that the extra terms of total angular momentum appear in Rashba current in addition to conventional one. 
Yi Li and Ruibao Tao