Spin polarization of electrons by reflection at a barrier
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Spintronics aims at using not only the electron's electric charge but also its quantum mechanical spin in order to develop novel device concepts beyond conventional charge-based electronics. Currently tremendous efforts are underway world-wide to achieve this goal and the theoretical research proposed here is part of it. In particular, the conditions are analyzed under which a device of nanometer size can deliver a beam of spin-oriented electrons using the spin-dependent reflection at a barrier. This work starts out from the fact that electrons can have two spin orientations, up and down. When the electrons in a tiny layer of a semiconductor like InSb hit a barrier, spin-up and spin-down electrons are reflected into different directions so that an appropriate set-up can select one or the other reflected beam. We study the conditions under which this set-up can be used to create a spin-polarized electron beam from a beam of initially unpolarized electrons. Inside the interference zone between the incoming and spin-flipped reflected beams parallel to the barrier, we get stripes of well-defined electron spin orientations.