Spin polarization of the asymmetric quantum point contact and conductance anomalies in the case of resonances

• Resonances substantially affect the spin polarization of the current.
• Localized spin–orbit interaction and resonances generate 0.5 conductance plateau.
• Significant spin polarization arises even in the one-electron approach.
• In the presence of resonances, the polarization increases due to the side voltage.
• We explain why 0.5 plateau appears only in the limited range of side gate values.

We study spin polarization and conductance of the asymmetric quantum point contact. We consider both Rashba coupling and lateral spin–orbit interaction induced by laterally asymmetric confinement potential. We show that in longitudinally symmetric quantum point contact, the spin polarization is not accompanied by the appearance of the conductance plateau at 0.5G00.5G0(G0=2e2/h)(G0=2e2/h). In longitudinally asymmetric quantum point contact the above plateau arises due to the presence of resonant states within the using one-electron approximation. An explanation of the experimental fact that the plateau exists only for a limited range of variation of the gate voltage is given.