  We demonstrate that non-equilibrium electrons in thin nonmagnetic
semiconductor layers or quantum dots can be fully spin polarized by means of
simultaneous electrical spin injection and extraction. The complete spin
polarization is achieved if the thin layers or quantum dots are placed between
two ferromagnetic metal contacts with moderate spin injection coefficients and
antiparallel magnetizations. The sign of the spin polarization is determined by
the direction of the current. Aplications of this effect in spintronics and
quantum information processing are discussed.

Other Condensed Matter