DC-CURRENT TRANSPORT AND AC JOSEPHSON EFFECT IN QUANTUM JUNCTIONS AT LOW-VOLTAGE

Multiple Andreev scattering in single-mode superconducting junctions w ith arbitrary normal electron transparency 0 < D < 1 is studied in the limit of low applied voltage eV much less than Delta. A quasiclassica l approach is developed for investigation of the dense lattice of inel astic sidebands associated with multiple Andreev scattering, which giv es a global description of inelastic-scattering amplitudes and spectra l distribution of the current. The crossover from the contact to the t unnel regime is investigated for the de current and ac Josephson curre nt as function of junction transparency and applied voltage. A mesosco pic: interference effect in junctions with intermediate transparency i s discussed. This effect shows up in oscillating features of the curre nt of thermal excitations.