Transport through a double quantum dot system with non-collinearly polarized leads

TL;DR

This paper analyzes electron transport in a double quantum dot system connected to spin-polarized leads, revealing how conductance peaks and tunneling magneto resistance depend on polarization angles, magnetic fields, and bias regimes.

Contribution

It provides an analytic study of linear and nonlinear transport, including conductance, spin accumulation, and TMR, with new insights into effects of non-collinear lead magnetizations and magnetic fields.

Findings

Conductance peaks vary with gate voltage and polarization angle.

Negative differential conductance appears in nonlinear regime for non-collinear magnetizations.

TMR remains positive in sequential tunneling but can become negative with an added magnetic field.

Abstract

We investigate linear and non-linear transport in a double quantum dot system weakly coupled to spin-polarized leads. In the linear regime, the conductance as well as the non-equilibrium spin accumulation are evaluated in analytic form. The conductance as a function of the gate voltage exhibits four peaks of different height, with mirror symmetry with respect to the charge neutrality point. As the polarization angle is varied, the position and shape of the peaks changes in a characteristic way which preserves the electron-hole symmetry of the problem. In the nonlinear regime negative differential conductance features occur for non collinear magnetisations of the leads. In the considered sequential tunneling limit, the tunneling magneto resistance (TMR) is always positive with a characteristic gate voltage dependence for non-collinear magnetization. If a magnetic field is added to the system, the TMR can become negative.