Effect of quantum fluctuations of the environment on the Coulomb blockade in a single barrier

The current-voltage characteristics of a single tunneling barrier are studied on a two-dimensional electron gas at millikelvin temperatures. As the impedance of the leads is gradually increased, the zero-bias differential resistance of the barrier increases and the tunneling current at low bias is suppressed (Coulomb blockade) in a power-law fashion. The data are in a quantitative agreement with the model in which quantum fluctuations of the environment enhance the tunneling rate. The linear I-V found at the lowest bias signalizes the breakdown of the simple theory, probably due to disorder. © 1993 The American Physical Society.