Electrically controlled spin polarization in suspended GaAs quantum point contacts

We report on the observation of the lateral electric spin polarization effect in a suspended GaAs-based quantum point contact (QPC) separated from the substrate. The effect manifests itself in the experiment as the appearance of an additional half-integer plateaus at 0.5×2e ²/h when the asymmetric voltage is applied to the side gates in zero magnetic field. The appearance of the plateaus has been attributed to the spin degeneracy lifting caused by the spin-orbit coupling associated with the lateral electric field in the asymmetrically biased QPC. We have experimentally demonstrated that, despite the relatively small g-factor in GaAs, the observation of the spin polarization in the GaAs-based QPCs becomes possible after the suspension due to the enhancement of the electron-electron interaction and the effect of the electric field guiding. These features are caused by a partial confinement of the electric field lines within a suspended semiconductor layer with a high dielectric constant. (paper)