SINGLE-ELECTRON BOX AND THE HELICITY MODULUS OF AN INVERSE-SQUARE XY MODEL

We calculate the average number of electrons on a metallic single-elec tron box as a function of the gate voltage for arbitrary values of the tunneling conductance. In the vicinity of the plateaus the problem is equivalent to calculating the helicity modulus of a classical inverse square XY model in one dimension. By a combination of perturbation th eory, a two-loop renormalization group calculation, and a Monte Carlo simulation in the intermediate regime we provide a complete descriptio n of the smearing of the Coulomb staircase at zero temperature with in creasing conductance.