Spin transport properties of a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations

TL;DR

This paper derives a comprehensive formula for spin current in a quantum dot with ferromagnetic leads at arbitrary angles, revealing complex angle-dependent behaviors influenced by Coulomb interactions.

Contribution

It introduces a general formula for spin current in interacting quantum dots with noncollinear ferromagnetic leads, accounting for Coulomb blockade effects.

Findings

Spin current component J_{z} can change sign depending on the angle θ.

Spin current and magnetoresistance show different angle dependence in different regimes.

An anomaly in angle dependence of spin current arises due to spin precession and spin-valve effects.

Abstract

A correct general formula for the spin current through an interacting quantum dot coupled to ferromagnetic leads with magnetization at an arbitrary angle $\theta$ is derived within the framework of the Keldysh formalism. Under asymmetric conditions, the spin current component J_{z} may change sign for $0<\theta<\pi$. It is shown that the spin current and spin tunneling magnetoresistance exhibit different angle dependence in the free and Coulomb blockade regimes. In the latter case, the competition of spin precession and the spin-valve effect could lead to an anomaly in the angle dependence of the spin current.