Effects of Conduction Electron Band Structure on Transport of Quantum Dot Systems

We study the effects of the energy band structure of conduction-electron on the transport properties of an interacting quantum dot system.By applying the nonequilibrium Keldysh Green function technique,we show that the finte width of electron band in leads causes the negative differential conductance in some regions of the applied voltage.We also show that the van Hove singulartites in the density of stated of conduction-electreon do not qualitatively change the differential conductance of the system,and hence can be safely ignored.Therefore,the wide band approximation used in the previous investigations is partially justified.