The role of the indirect tunneling processes and asymmetry in couplings in orbital Kondo transport through double quantum dots

Abstract: System of two quantum dots attached to external electrodes is considered theoretically in orbital Kondo regime. In general, the double dot system is coupled via both Coulomb interaction and direct hoping. Moreover, the indirect hopping processes between the dots (through the leads) are also taken into account. To investigate system's electronic properties we apply slave-boson mean field (SBMF) technique. With help of the SBMF approach the local density of states for both dots and the transmission (as well as linear and differencial conductance) is calculated. We show that Dicke- and Fano-like line shape may emerge in transport characteristics of the double dot system. Moreover, we observed that these modified Kondo resonances are very susceptible to the change of the indirect coupling's strength. We have also shown that the Kondo temperature become suppressed with increasing asymmetry in the dot-lead couplings when there is no indirect coupling. Moreover, when the indirect coupling is turned on the Kondo temperature becomes suppressed. By allowing a relative sign of the nondiagonal elements of the coupling matrix with left and right electrode, we extend our investigations become more generic. Finally, we have also included the level renormalization effects due to indirect tunneling, which in most papers is not taken into account.