Multiorbital Kondo effect in quantum dots coupled to ferromagnetic leads

We investigate the Kondo effect of a multiorbital quantum dot coupled to ferromagnetic leads, using an equation of motion method. It is shown that the Kondo peak splits into three peaks and the middle one is located close to the Fermi energy. As the spin polarization of the leads is increased, the splitting between the highest and lowest energy peaks increases. The results indicate that the Kondo effect caused by the orbital degrees of freedom remains, while the Kondo effect caused by the spin degrees of freedom is suppressed. The origin of the suppressed spin Kondo effect is discussed in terms of the renormalized energy level of the quantum dot.