All-electric spintronics with quantum point contacts

We review our recent study of the conductance of side gated quantum point contacts (QPCs) in the presence of lateral spin-orbit scattering (LSOC). As shown in Phys. Rev. B 80, 155440 (2009), a small difference of bias between the two side gates of a QPC leads to an inversion asymmetry in the LSOC on opposite edges of the channel. This triggers a small spin imbalance in the QPC. The latter increases substantially when the effects of electron-electron interaction are included in the QPC. This is accompanied by a wide variety of anomalous conductance plateaus as the dimensions of the QPC are varied. In this paper, the spin polarization of the conductance a is studied as a function of the device geometry. A simple model of two QPCs in series predict an ON/OFF ratio equal to 1/(1 - α
²
) which is around 86 at T = 4.2K for the device parameters investigated. A tandem of QPCs could therefore act as an efficient all-electric spin valve. Design issues for operation at higher temperature are discussed.