Cotunneling assisted sequential tunneling in multilevel quantum dots

We investigate the conductance and zero-frequency shot noise of interacting, multilevel quantum dots coupled to leads. We observe that cotunneling assisted sequential tunneling (CAST) processes play a dominant role in the transition region from Coulomb blockade to sequential tunneling. We analyze for intermediate coupling strength the dependence of the conductance due to CAST processes on temperature, coupling constant, and gate voltage. Remarkably, the width of the CAST transport feature scales only with temperature, but not with the coupling constant. While the onset of inelastic cotunneling is associated with a super-Poissonian noise, the noise is even stronger above the threshold for CAST processes. (C) 2008 American Institute of Physics.