  We model a Superconducting Single-Electron Transistor operating by repulsive
interactions. The device consists of a ring of Hubbard clusters, placed between
electrodes and capacitively coupled to a gate potential. In each cluster, a
pair of electrons at appropriate filling feels a weak effective interaction
which leads to pairing in part of the parameter space. Thus, the system can
host many bound pairs, with correlation induced binding. When the charging
energy exceeds the pairing energy, single-electron tunneling prevails; in the
opposite regime, we predict the Coulomb blockade pattern of two-electron
tunneling. This suggests that in tunneling experiments repulsion-induced pairs
may behave in a similar way as phonon-induced ones.
