Cotunneling through a quantum dot coupled to ferromagnetic leads with noncollinear magnetizations

TL;DR

This paper theoretically investigates spin-dependent electron transport through a quantum dot with noncollinear ferromagnetic leads, analyzing how magnetic orientation affects current, conductance, and magnetoresistance in the cotunneling regime.

Contribution

It introduces a model for cotunneling in a quantum dot with noncollinear ferromagnetic leads, considering arbitrary Coulomb interactions and spin splitting, and explores angular dependencies of transport properties.

Findings

Electric current varies with the angle between magnetic moments.

Tunnel magnetoresistance depends on magnetic orientation.

The cotunneling gap evolves with magnetic angle and level splitting.

Abstract

Spin-dependent electronic transport through a quantum dot has been analyzed theoretically in the cotunneling regime by means of the second-order perturbation theory. The system is described by the impurity Anderson Hamiltonian with arbitrary Coulomb correlation parameter $U$. It is assumed that the dot level is intrinsically spin-split due to an effective molecular field exerted by a magnetic substrate. The dot is coupled to two ferromagnetic leads whose magnetic moments are noncollinear. The angular dependence of electric current, tunnel magnetoresistance, and differential conductance are presented and discussed. The evolution of a cotunneling gap with the angle between magnetic moments and with the splitting of the dot level is also demonstrated.