COTUNNELING AT RESONANCE FOR THE SINGLE-ELECTRON TRANSISTOR

We study electron transport through a small metallic island in the per turbative regime. Using a diagrammatic real-time technique, we calcula te the occupation of the island as well as the conductance through the transistor to fourth order in the tunneling matrix elements, a proces s referred to as cotunneling. Our formulation does not require the int roduction of a cutoff. At resonance we find deviations from previous t heories and quantitative agreement with recent experiments.