Enhanced spin injection efficiency in a four-terminal double quantum dot system

TL;DR

This paper demonstrates that a double quantum dot system with four ferromagnetic terminals can significantly enhance spin injection efficiency due to exchange interactions, outperforming single-dot configurations.

Contribution

It introduces a novel double quantum dot setup with four ferromagnetic terminals that improves spin injection efficiency via exchange interactions.

Findings

Spin injection efficiency is significantly improved in the double dot system.

Antiparallel magnetization configuration enhances polarization rate in one dot.

Exchange interaction is key to the improved spin injection performance.

Abstract

Within the scheme of quantum rate equations, we investigate the spin-resolved transport through a double quantum dot system with four ferromagnetic terminals. It is found that the injection efficiency of spin-polarized electrons can be significantly improved compared with single dot case. When the magnetization in one of four ferromagnetic terminals is antiparallel with the other three, the polarization rate of the current through one dot can be greatly enhanced, accompanied by the drastic decrease of the current polarization rate through the other one. The mechanism is the exchange interaction between electrons in the two quantum dots, which can be a promising candidate for the improvement of the spin injection efficiency.