Spatial interference induced spin polarization in a three-terminal quantum ring

A one-dimensional three-terminal mesoscopic ring, in the presence of Rashba spin–orbit interaction can act as an electron spin beam splitter: In the ballistic regime different spin polarizations can be achieved in the two output channels of the ring from an originally totally unpolarized incoming spin state. We analyze the physical origin of this polarizing effect, and find that it is a result of an appropriate interference of states that carry oppositely directed currents. We visualize the stationary spin directions along the ring for an originally totally spin-unpolarized electron, revealing the interference induced formation of the pure spin states on the outputs.