Spin current manipulation through a Rashba dot by tunable nonequilibrium Fano-Kondo effect

Abstract

Abstract. Though the Rashba-type spin-orbit interaction offers a possibility of manipulating electron's spin totally by electric field, it has been argued that the mere existence of spinorbit interaction is insufficient to produce such spin-dependent transport. In the present work, we investigate how spin transport through a single-level dot is possible: Finite spin current appears as a result of spin-orbit interaction, strong electronic correlation and finite bias voltage. We show, by applying finite interaction slave-boson mean field theory, that Kondo physics is responsible for generating such spin-dependent transport. IntroductionIn semiconducting devices, the Rashba-type spin-orbit interaction is generated by the potential asymmetry in the direction perpendicular to the semiconductor plane. Utilizing the effect opens up a possibility of controlling electron's spin totally by electric field alone. It has been argued, however, that the Rashba-type spin-orbit interaction alone is insufficient to realize finite spin transport or spin filtering effect. Because of it, there have been various suggestions how to attain spin transport by combining with other effect such as magnetic field, finite bias effect [1,2,3,4]. So far nonetheless, electrically generated spin-dependent transport due to many-body effect remains largely unexplored.In the present work, we investigate the electric generation of spin current and transport through an interacting Rashba dot (a dot with the Rashba spin-orbit interaction and the Coulomb interaction) embedded in a ring geometry. We will show that spin transport can manifest itself electrically once the following three conditions are met: (1) strong Coulomb interaction is present on the dot (2) under finite bias voltage V bias (3) at very low temperature T . Having the characteristic temperature of the system (= the Kondo temperature) seriously affected by the presence of the Rashba interaction and the Coulomb interaction, we need to treat both effects in a unified way. We argue that many-body effect responsible for generating spin current originates from Kondo physic, so that either too large bias voltage or temperature destroys the effect.