Influence of an external voltage on the conductance through a quantum dot side-coupled to a short quantum wire

We investigate, the, influence of an external voltage V-0 on conductance G through a quantum dot (QD), which is side-coupled to a quantum wire of length L-W, whose two ends are weakly connected to leads. In our calculation, the poor man's scaling law and slave-boson mean-field method are employed. With V0 increased, a series of resonant regions is formed and G exhibits different properties in and out of these regions, which is the universal result of the finite-size effect on the Kondo correlation. In symmetric structures, the would-be resonant regions. corresponding to odd wavefunctions are removed. If the symmetry is broken by changing the QD position, those regions will be recovered. In two asymmetric structures with their wire lengths being L-W and L-W + 1, respectively, the two sets of resonant regions intersect with each other. These-symmetry-related phenomena characterize side-coupled QD structures. With the barrier width increased, the number of resonant regions is increased,too.