Models of a multi-terminal spin filter using a quantum dot with SO interaction. (a) Impurity Anderson model with three leads. There are two energy levels (j = 1, 2) in the quantum dot. They are connected to lead by tunnel coupling, V
(b) A three-terminal spin-filtering device fabricated on semiconductor heterostructures. 2DEG is confined in the xy plane. A quantum dot is formed by quantum point contacts on three leads. Reservoir S is a source from which spin-unpolarized electrons are injected into the quantum dot. The voltage is identical in reservoirs D1 and D2.