Spin transmission through a mesoscopic zigzag Rashba wire

The ballistic transport through a mesoscopic zigzag Rashba wire is studied via the Green function technique and the spin transmission is investigated with an unpolarized charge current injected. These results are compared with those of a straight wire, and show that to generate a nonzero spin conductance in the longitudinal direction, the mirror symmetry with respect to that direction must be broken. This necessary condition is satisfied in the zigzag wire. Its ballistic transport properties are also affected by the spin-dependent quantum interference effect, resulting from the Rashba spin-orbit coupling and scattering at corners and at interfaces between the wire and the leads. Mixing between different pairs of transverse modes is crucial for spin transmission, and only if more than one pair of modes are open can a measurable spin-polarized current be obtained in the longitudinal direction. These results provide one way to generate an artificially controllable spin-polarized current in mesoscopic Rashba systems