Spin-transistor action in waveguides with periodically modulated strength of the spin–orbit interaction

Spin-polarized electron transport through waveguides, in which the strength of the spin–orbit interaction (SOI) α is varied periodically, is studied using the transfer-matrix technique. In a waveguide in which the SOI exists only in one segment, the total transmission shows a sinusoidal dependence on the strength α and the segment length l. The modulated total transmission T works as the envelope of the spin-up (T+) or spin-down (T−) electron transmission in the manner View the MathML source and View the MathML source, where θ is a measure of the precession. In a periodically modulated waveguide, with two subunits in each unit cell of different strength, the total transmission is further modulated and gaps appear when the strength α or the length of one of the two subunits is varied, provided only one mode is allowed to propagate in the waveguide. A similar but not periodic behavior occurs as a function of the incident electron energy. The structure considered is a good candidate for the establishment of a realistic spin transistor.