3e tunneling processes in a superconducting single-electron tunneling transistor

A current due to a tunneling event that involves three times the charge of an electron was observed in the current-voltage characteristics of a superc onducting single-electron tunneling transistor. Ln this tunnel event, a Coo per pair tunnels through one tunnel barrier simultaneously with a quasipart icle that tunnels through a second tunnel barrier which is about 0.5 mu m d istant from the first tunnel barrier. This current was observed in a bias r egime where current flow due to sequential quasiparticle tunneling is forbi dden due to the Coulomb blockade. [S0163-1829(98)01347-2].