Symmetries and couplings in double quantum dot molecule

Electronic transport through a quantum dot molecule attached to leads has been very successfully studied finding very interesting effects like Fano and Kondo. In particular, the symmetry in quantum dot molecules going from the parallel to series coupling seems to play a very interesting role showing very different density of states spectra, these results have been obtained by fixing the interdot coupling equal to the coupling to the leads. In this work we go a step further by changing the value of the interdot coupling and the addition of on-site Coulomb interaction with the help of Slave Boson Mean Field theory (SBMFT), Keldysh non equilibrium Green function technique and the equation of motion approach the density of states and the conductance of this system are calculated and analyzed in the Kondo regime. We also studied the asymmetric molecule set up of dots of different size in order to analyze the density of states and the Fano interference in an anticrossing region. Comparison of the results taking into account the Coulomb interaction is presented, which gives rise to the appearance of the Kondo effect in these systems. We also studied the interplay between the Kondo and Fano effects. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.