Tunneling current through multiple degenerate states of individual quantum dots

A multilevel Anderson model is employed to simulate the system composed of a quantum dot connected with metallic electrodes. The inhomogenous electron Coulomb interactions in the dot are taken into account in the calculation Of tunneling current by the nonequilibrium Green's function technique. In the Coulomb blockade regime, all n-fold degenerate state exhibits the periodic oscillation of n peaks with respect to the gate voltage for homogenous electron Coulomb interaction, but not a periodic structure for inhomogeneous interactions. The well-known staircase behavior arising from not only intraorbital Coulomb interactions but also interorbital interactions is observed in the tunneling current. We also observe the tunneling current showing negative differential conductances instead of bistable Current in the attractive interorbital interactions.