Spin-polarized transport through a single-level quantum dot in the Kondo regime

Abstract

Nonequilibrium electronic transport through a quantum dot coupled to ferromagnetic leads(electrodes) is studied theoretically by the nonequilibrium Green function technique. Thesystem is described by the Anderson model with arbitrary correlation parameterU. Exchange interaction between the dot and ferromagnetic electrodes is taken into account via an effective molecular field. The following situations are analysed numerically:(i) the dot is symmetrically coupled to two ferromagnetic leads, (ii) one of thetwo ferromagnetic leads is half-metallic with almost total spin polarization ofelectron states at the Fermi level, and (iii) one of the two electrodes is nonmagneticwhereas the other one is ferromagnetic. Generally, the Kondo peak in the density ofstates (DOS) becomes spin-split when the total exchange field acting on the dot isnonzero. The spin-splitting of the Kondo peak in DOS leads to splitting andsuppression of the corresponding zero-bias anomaly in the differential conductance.