Charge and spin currents in a three-terminal mesoscopic ring

We theoretically investigate the charge and spin currents in a three-terminal mesoscopic ring in the presence of a uniform and nonuniform Rashba spin-orbit interaction (SOI). It is shown that a fully spin-polarized charge current and a pure spin current can be generated by tuning the probe voltages and/or the strength of the Rashba SOI. The charge and spin currents oscillate as the strength of the Rashba SOI increases induced by the spin quantum interference. The ratio of probe voltages oscillates synchronously with the pure spin current as the strength of the Rashba SOI increases in a nonuniform Rashba ring, while it remains constant in a uniform Rashba ring. We demonstrate theoretically that a three-terminal uniform Rashba ring can be used as a spin polarizer and/or spin flipper for different spin injections, and a nonuniform Rashba ring could allow us to detect the pure spin current electrically. (C) 2009 American Institute of Physics. [DOI 10.1063/1.3054322