OBSERVATION OF THE EFFECT OF AN ELECTROMAGNETIC ENVIRONMENT WITH SHARP RESONANCES ON THE CURRENT-VOLTAGE CHARACTERISTIC OF A SMALL CAPACITANCE TUNNEL JUNCTION

We have measured the current-voltage characteristic of a small capacit ance tunnel junction coupled to a transmission line resonator. We cali brate the resonator using the sharp resonances displayed by the juncti on in the superconducting state, which correspond to the pumping of th e modes of the resonator by the AC Josephson current. With this calibr ation, we explain quantitatively the non-linearity of the junction cha racteristic in the normal state as being due to the process by which a single electron tunnels by emitting a photon, the basic process of th e theory of the effect of the electromagnetic environment on tunneling .