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# Secondary “smile”-gap in the density of states of a diffusive Josephson junction for a wide range of contact types

Type of Publication: | Journal article |

Author: | Reutlinger, Johannes; Glazman, Leonid; Nazarov, Yu V.; Belzig, Wolfgang |

Year of publication: | 2014 |

Published in: | Physical Review B ; 90 (2014), 1. - 014521. - ISSN 0163-1829. - eISSN 1095-3795 |

DOI (citable link): | https://dx.doi.org/10.1103/PhysRevB.90.014521 |

Summary: |
The superconducting proximity effect leads to strong modifications of the local density of states in diffusive or chaotic cavity Josephson junctions, which displays a phase-dependent energy gap around the Fermi energy. The so-called minigap of the order of the Thouless energy E
_{Th} is related to the inverse dwell time in the diffusive region in the limit E_{Th}≪Δ, where Δ is the superconducting energy gap. In the opposite limit of a large Thouless energy E_{Th}≫Δ, a small new feature has recently attracted attention, namely, the appearance of a further secondary gap, which is around two orders of magnitude smaller compared to the usual superconducting gap. It appears in a chaotic cavity just below the superconducting gap edge Δ and vanishes for some value of the phase difference between the superconductors. We extend previous theory restricted to a normal cavity connected to two superconductors through ballistic contacts to a wider range of contact types. We show that the existence of the secondary gap is not limited to ballistic contacts, but is a more general property of such systems. Furthermore, we derive a criterion which directly relates the existence of a secondary gap to the presence of small transmission eigenvalues of the contacts. For generic continuous distributions of transmission eigenvalues of the contacts, no secondary gap exists, although we observe a singular behavior of the density of states at Δ. Finally, we provide a simple one-dimensional scattering model which is able to explain the characteristic “smile” shape of the secondary gap. |

Subject (DDC): | 530 Physics |

Bibliography of Konstanz: | Yes |

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REUTLINGER, Johannes, Leonid GLAZMAN, Yu V. NAZAROV, Wolfgang BELZIG, 2014. Secondary “smile”-gap in the density of states of a diffusive Josephson junction for a wide range of contact types. In: Physical Review B. 90(1), 014521. ISSN 0163-1829. eISSN 1095-3795. Available under: doi: 10.1103/PhysRevB.90.014521

@article{Reutlinger2014Secon-29743, title={Secondary “smile”-gap in the density of states of a diffusive Josephson junction for a wide range of contact types}, year={2014}, doi={10.1103/PhysRevB.90.014521}, number={1}, volume={90}, issn={0163-1829}, journal={Physical Review B}, author={Reutlinger, Johannes and Glazman, Leonid and Nazarov, Yu V. and Belzig, Wolfgang}, note={Article Number: 014521} }