Josephson effect and quantum fluctuations

Phase fluctuations destroy the DC Josephson effect and replace the supercur rent at zero voltage by a peak at small but finite voltages. We study the e ffect of quantum fluctuations of the phase at zero temperature by accountin g for a finite junction capacitance and an environmental resistance. The Jo sephson peak is expressed analytically by two complementary expansions. Thi s result establishes the connection between the regimes of classical phase diffusion, Coulomb blockade and macroscopic quantum tunneling. (C) 2000 Els evier Science B.V. All rights reserved.