Strong Tunneling in the Single-Electron Transistor

We have investigated the suppression of single-electron charging effects in metallic single-electron transistors when the conductance of the tunnel junctions becomes larger than the conductance quantum $e^2/h$. We find that the Coulomb blockade of the conductance is progressively shifted at lower temperatures. The experimental results agree quantitatively with the available $1/T$ expansion at high temperature, and qualitatively with the predictions of an effective two-state model at low temperature, which predicts at $T=0\mathrm{}$ a blockade of conductance for all gate voltages.