Coherent transport through T-shaped electrostatically coupled quantum dots

The Fano–Kondo resonance is studied in a system consisting of a pair of side-coupled double quantum dots attached to quantum wires. The double dots are capacitively coupled. The mean field slave boson approach and the equation of motion method are used. For symmetric dots Kondo effect has two possible sources: spin and charge degeneracies. The conductance as a function of gate voltage is characterized by a Fano asymmetric parameter q. For q=0 a half-reflection is observed. The same value of transmission is expected in the limit q→∞. For intermediate cases transmission line has a general asymmetric Fano-type shape. We show that by tuning the gate voltage or changing magnetic field, the single spin-orbital Kondo channel opens and the system can operate as a spin filter.