Spin transport of electrons and holes in a metal and in a semiconductor

The features of the spin and charge transport of electrons and holes in a metal and a semiconductor were studied using the Boltzmann transport equations. It was shown that the electrons and holes carry the spin in opposite directions in an electrical current. As result, the spin polarization of an electrical current in a metal is substantially smaller than spin polarization of electron gas. It was shown that the spin properties of the electron gas are responsible for the existence of the concept of "electrons" and "holes" in a metal and a semiconductor.