Abstract
•Multifunctional spin polarizer based on a side-coupled double quantum dot molecule is implemented.•Bidirectional and dual spin polarizers are realized without switching the direction of the magnetic field.•The polarizing scenarios could be controlled easily by the initial charge state through external gate voltage.•The spin polarizer reveals almost 100% efficiency.
Quantum dot system is considered as the prime candidate for nanospintronics devices, within which to generate spins one by one is the long term goal for quantum information and quantum computation. In this paper, with the aid of the Wilson’s numerical renormalization group method, we find a side-coupled double quantum dot molecule could be used to implement a multifunctional spin polarizer in the strongly correlated regime without switching the direction of the magnetic field. The spin polarizer reveals almost 100% efficiencies, and the polarizing scenarios could be controlled easily by the initial charge state through external gate voltage, leading to various kinds of spin polarizers, e.g., unidirectional, bidirectional, and dual spin polarizers. We demonstrate the Zeeman effect and the inter-dot transport processes are responsible for the spin-polarized transport. Our scheme is robust for any inter-dot coupling and may also be useful for quantum dots connected with magnetic leads.