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

摘要

We study the Kondo effect in a quantum dot coupled to half-metallic ferromagnetic electrodes in the regime of strong on-dot correlations. Using the equation of motion technique for non-equilibrium Green functions in the slave boson representation, we show that the Kondo effect is not completely suppressed for anti-parallel magnetization of the leads. In the parallel configuration, there is no Kondo effect but there is an effect associated with 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 the temperature-dependent resonance at the Fermi energy, which splits with the bias voltage and the magnetic field. Moreover, unlike for non-magnetic or not fully polarized ferromagnetic leads, only the minority spin electrons can form such resonance in the density of states. However, this resonance cannot be observed directly in the transport measurements, and we give some clues how to identify the effect in such systems.