Nonlinear Spin Polarized Transport Through a Quantum Dot

TL;DR

This paper provides a theoretical analysis of nonlinear spin-polarized transport in a quantum dot spin-valve device, deriving formulas for current and tunneling magnetoresistance, and explaining temperature-dependent conductance behavior.

Contribution

It introduces a closed-form formula for current in a quantum dot spin-valve, including Coulomb interactions, and reports exact nonlinear I-V characteristics and conductance slopes.

Findings

Exact nonlinear I-V curves for TMR junctions as a function of angle θ

Conductance slope at zero bias varies with temperature, matching experimental anomalies

Explicit inclusion of Coulomb interaction at Hartree level in the model

Abstract

We present a theoretical analysis of the nonlinear bias and temperature dependence of current-voltage characteristics of a spin-valve device which is formed by connecting a quantum dot to two ferromagnetic electrodes whose magnetic moments orient at an angle $\theta$ with respect to each other. The theory is based on nonequilibrium Green's function approach and focused on current perpendicular to plane geometry. Coulomb interaction has been taken into account explicitly at the Hartree level. We derive a formula in closed form for current flowing through the device in general terms of bias and temperature. In the wideband limit we report exact results for the TMR junction nonlinear I-V curve as a function of $\theta$. We also report the conductance slope at zero bias as a function of temperature for which experimental results reported an anomalous behavior.