title: "Smile" gap in the density of states of a cavity between superconductors.
abstract: The density of Andreev levels in a normal metal (N) in contact with two superconductors (S) is known to exhibit an induced minigap related to the inverse dwell time. We predict a small secondary gap just below the superconducting gap edge-a feature that has been overlooked so far in numerous microscopic studies of the density of states in S-N-S structures. In a generic structure with N being a chaotic cavity, the secondary gap is the widest at zero phase bias. It closes at some finite phase bias, forming the shape of a "smile". Asymmetric couplings give even richer gap structures near the phase difference π. All the features found should be amendable to experimental detection in high-resolution low-temperature tunneling spectroscopy.
authors.affiliation: Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Reutlinger
authors.affiliation: Department of Physics, Yale University, New Haven, Connecticut 06511-8499, USA.
authors.forename: L
authors.initials: L
authors.lastname: Glazman
authors.affiliation: Kavli Institute of Nanoscience Delft, Delft University of Technology, 2628 CJ Delft, Netherlands.
authors.forename: Yu V
authors.initials: YV
authors.lastname: Nazarov
authors.affiliation: Fachbereich Physik, Universität Konstanz, D-78457 Konstanz, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Belzig