Kondo transport through serially coupled triple quantum dots

The equilibrium and nonequilibrium Kondo transport properties of the serially coupled triple quantum dots (TQD's), including one intermediate dot and two peripheral dots, were studied theoretically. As the Kondo resonance is strongly renormalized in a nontrivial manner by the interdot coupling, the zero-bias conductance shows an asymmetrical double-peak pattern, which is significantly different from the single-conductance-peak pattern that appeared in the TQD device in the Coulomb regime. Furthermore, in the finite-bias case, the current versus the bias shows a peak and a relatively large negative differential conductance is observed. In addition, the superposition of the Kondo spin singlet and the usual naked state is also investigated and strong mixture between them is observed even though they belong to different kinds of states.