Bipolar spin switch using Aharonov-Bohm ring with embedded double quantum dots

We report on the analysis of quantum transport through an Aharonov-Bohm ring with embedded double quantum dots. The normal metal leads are assumed to be weakly coupled to the two quantum dots. In the quantum dot region, Rashba spin-orbit coupling and electron-electron interaction are considered. The quantum transport is analyzed based on the Keldysh nonequilibrium Green's function formalism. A spin-polarized current emerges in this device due to the combined effect of a magnetic flux, threading through the AB ring, and the Rashba spin-orbit coupling. An interesting switching property of the spin polarization by turning on and off the gate within small voltage window is observed. This feature, however, does not exist in the Aharonov-Bohm ring structure with single quantum dot. We therefore propose a theoretical idea of a bipolar spin polarization switch.