Residual Kondo effect in quantum dot coupled to half-metallic ferromagnets

Abstract

We study the Kondo effect in a quantum dot coupled to half-metallic ferromagneticelectrodes in the regime of strong on-dot correlations. Using the equation of motiontechnique for non-equilibrium Green functions in the slave boson representation, we showthat the Kondo effect is not completely suppressed for anti-parallel magnetization of theleads. In the parallel configuration, there is no Kondo effect but there is an effect associatedwith elastic co-tunnelling which, in turn, leads to similar behaviour of the local (on-dot)density of states (LDOS) as the usual Kondo effect. Namely, the LDOS shows thetemperature-dependent resonance at the Fermi energy, which splits with the bias voltageand the magnetic field. Moreover, unlike for non-magnetic or not fully polarizedferromagnetic leads, only the minority spin electrons can form such resonance in thedensity of states. However, this resonance cannot be observed directly in the transportmeasurements, and we give some clues how to identify the effect in such systems.