Spin effects in electron tunnelling through a quantum dot coupled to non-collinearly polarized ferromagnetic leads

TL;DR

This paper theoretically investigates how spin precession and Coulomb interactions influence electron tunneling in a quantum dot with ferromagnetic leads, revealing effects like negative differential conductance and angular current variations.

Contribution

It introduces a detailed analysis of spin effects in non-collinear ferromagnetic quantum dot tunneling using nonequilibrium Green functions, highlighting new spin precession phenomena.

Findings

Coulomb correlations enhance spin precession.

Spin precession can cause negative differential conductance.

Angular current variation and TMR sign change are observed.

Abstract

Spin-dependent transport through an interacting single-level quantum dot coupled to ferromagnetic leads with non-collinear magnetizations is analyzed theoretically. The transport properties and average spin of the dot are investigated within the nonequilibrium Green function technique based on the equation of motion in the Hartree-Fock approximation. Numerical results show that Coulomb correlations on the dot and strong spin polarization of the leads significantly enhance precession of the average dot spin around the effective molecular field created by the external electrodes. Moreover, they also show that spin precession may lead to negative differential conductance in the voltage range between the two relevant threshold voltages. Nonmonotonous angular variation of electric current and change in sign of the tunnel magnetoresistance are also found. It is also shown that the diode-like behavior in asymmetrical junctions with one electrode being half-metallic is significantly reduced in noncollinear configurations.