Spin Transport in a Rashba Ring-Quantum Dot System Pumped by Microwave Fields

We report a theoretical study on producing electrically spin-polarized current in the Rashba ring withparallel double dots embedded,which are subject to two time-dependent microwave fields.By means of the KeldyshGreen’s function method,we present an analytic result of the pumped current at adiabatic limit and demonstrate thatthe interplay between the quantum pumping effect and spin-dependent quantum interference can lead to an arbitrarilycontrollable spin-polarized current in the device.The magnitude and direction of the charge and spin current can beeffectively modulated by system parameters such as the pumping phase difference,Rashba precession phase,and thedynamic phase difference of electron traveling in two arms of ring; moreover,the spin-polarization degree of the chargecurrent can also be tuned in the range [-∞,+∞].Our findings may shed light on the all-electric way to produce thecontrollable spin-polarized charge current in the field of spintronics.