Charge quantization in S-I-N Coulomb blockade structures

We study the crossover between the Coulomb blockade and proximity-induced s uperconductivity in a small normal island connected by a tunnel junction to a superconducting lead. Unlike the N-I-N case, the steps of the Coulomb st aircase remain sharp even if the conductance of the tunneling barrier excee ds e(2)/h. The crossover occurs only at a larger conductance, G* similar to (e(2)/h) root Delta/delta, where Delta and delta are the superconducting g ap and average level spacing in the lead and island respectively. (C) 2001 Elsevier Science B.V. All rights reserved.