Spin polarized current in a quantum dot connected to a spin-orbit interacting Fermi sea

Abstract

In this study, we investigate the transport properties of a device comprising a quantum dot (QD) connected to a Rashba spin-orbit interacting nanoribbon, which is spontaneously magnetically polarized or deposited on a ferromagnetic substrate. The QD is as well connected to two other lateral contacts along which the electronic current circulates. One contact comprising the source of electrons is ferromagnetic, whereas the other contact comprising , the drain, could be a non-magnetic or a ferromagnetic metal with anti-parallel magnetization relative to the source contact polarization. The connection of the QD local state to the Fermi sea under the effect of spin-orbit coupling (SOC) creates a spin-flip mechanism that affects the electronic spins circulating along the device. This process is tuned by the QD gate voltage and it is strongly enhanced when the Fermi energy of the system is in the neighborhood of a Van-Hove singularity of the SOC Fermi sea band. The spin-flip of the incident polarized current can be controlled by manipulating the gate potential of the QD. We show that this system possesses all the requirements necessary to operate as a spin transistor.Due to the local character of the QD level, the Coulomb interaction plays an important role. It enhances the parameter region within which the spin transistor can operate. The effects of the intra-dot Coulomb interaction are analyzed within the context of the alloy analogy Hubbard III approximation, which provides an adequate understanding of the Coulomb blockade transport properties above the Kondo temperature.