Superconducting single-charge transistor in a tunable dissipative environment

We investigate a superconducting single-charge transistor, which is capacit ively coupled to an ohmic two-dimensional electron gas, whose resistivity c an be controlled by a back gate and introduces an ohmic dissipative term fo r its dynamics. We show, how the coherence between the single-tunneling eve nts is destroyed by these fluctuations. We find various different regimes o f the system conductance G depending on the environment. (C) 2000 Elsevier Science B.V. All rights reserved.