0.7 anomaly due to the Rashba interaction in a nonuniform electric field

Abstract

We demonstrate that three conductance features, 0.5 and 0.7G(0) plateaus and a dip at 0.5G(0), observed in quantum point contacts (QPCs) can be consistently explained by the Rashba interaction in the nonuniform electric field created by the side gates along the transport direction. A quantity gamma is defined which depends on the extent of this nonuniformity and the electron density. A short QPC tends to have a small gamma. Only when gamma is large will the Rashba interaction produce a potential well deep enough to localize the electron. This provides the bound state that forms the Kondo resonance with the tunneling electrons. We propose to compare the medium/long QPC to small/large quantum dots, which are governed by the Kondo physics and the Coulomb blockade, respectively. The relation between 0.7 anomaly and the side-gate voltage, length of QPC, and temperature can all be determined to agree qualitatively with the experiments.