We present extensive experimental data on charge transport by Andreev reflection through a mesoscopic superconducting island coupled to two normal metal leads through small tunnel junctions and to a capacitive gate. The data show the systematic dependence on the gate-induced charge ${\mathit{Q}}_0$ of both the Coulomb blockade of Andreev reflection and of striking voltage thresholds that correspond to specific tunneling processes. The magnitude of this Andreev current and its dependence on ${\mathit{Q}}_0$ are in excellent agreement with recent theory, provided that interference between the two tunneling electrons is taken into account.

• Received 29 October 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.1742