Influence of quantum fluctuations on phase-coherent two-electron tunneling
I. Institut für Theoretische Physik, Jungiusstrasse 9,
D-20355 Hamburg, Germany
2 Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 OHE, United Kingdom
Accepted: 28 November 1997
We study the subgap transport properties of a small-capacitance normal-metal–superconductor tunnel junction coupled to an external electromagnetic environment. Mesoscopic interference between the electrons in the normal metal strongly enhances the subgap conductance with decreasing bias voltage. On the other hand, quantum fluctuations of the environment destroy electronic phase coherence and suppress the subgap conductance at low bias (Coulomb blockade). The competition between charging effects and mesoscopic interference leads to a non-monotonic dependence of the differential subgap conductance on the applied bias voltage. This feature is pronounced, even if the coupling to the environment is weak and the charging energy is small.
PACS: 74.50.+r – Proximity effects, weak links, tunneling phenomena, and Josephson effects / 72.10.Fk – Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
© EDP Sciences, 1998