中国物理B ›› 2017, Vol. 26 ›› Issue (3): 37401-037401.doi: 10.1088/1674-1056/26/3/037401

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

Validation of the Wiedemann-Franz law in a granular s-wave superconductor in the nanometer scale

A Yousefvand, H Salehi, M Zargar Shoushtari   

  1. Department of Physics, Shahid Chamran University of Ahvaz, Ahvaz, Iran
  • 收稿日期:2016-09-27 修回日期:2016-12-23 出版日期:2017-03-05 发布日期:2017-03-05
  • 通讯作者: A Yousefvand E-mail:a_yoosef@yahoo.com
  • 基金资助:

    Project supported by Shahid Chamran University of Ahvaz.

Validation of the Wiedemann-Franz law in a granular s-wave superconductor in the nanometer scale

A Yousefvand, H Salehi, M Zargar Shoushtari   

  1. Department of Physics, Shahid Chamran University of Ahvaz, Ahvaz, Iran
  • Received:2016-09-27 Revised:2016-12-23 Online:2017-03-05 Published:2017-03-05
  • Contact: A Yousefvand E-mail:a_yoosef@yahoo.com
  • Supported by:

    Project supported by Shahid Chamran University of Ahvaz.

摘要:

The present study tries to evaluate the validity of the Wiedemann-Franz law in a granular s-wave superconductor in the presence of concentrated impurities. By using Green's function method and the Kubo formula technique, three distinct contributions of the Aslamazov-Larkin, the Maki-Thompson and, the density of states are calculated for both the electrical conductivity and the thermal conductivity in a granular s-wave superconductor. It is demonstrated that these different contributions to the fluctuation conductivity depend differently on the tunneling because of their different natures. This study examines the transport in a granular superconductor system in three dimensions in the limit of large tunneling conductance, which makes it possible to ignore all localization effects and the Coulomb interaction. We find that the tunneling is efficient near the critical temperature and that there is a crossover to the characteristic behavior of a homogeneous system. When it is far from the critical temperature, the tunneling is not effective and the system behaves as an ensemble of real zero-dimensional grains. The results show that the Wiedemann-Franz law is violated in both temperature regions.

关键词: granular superconductor, s-wave, impurity vertex, fluctuation propagator

Abstract:

The present study tries to evaluate the validity of the Wiedemann-Franz law in a granular s-wave superconductor in the presence of concentrated impurities. By using Green's function method and the Kubo formula technique, three distinct contributions of the Aslamazov-Larkin, the Maki-Thompson and, the density of states are calculated for both the electrical conductivity and the thermal conductivity in a granular s-wave superconductor. It is demonstrated that these different contributions to the fluctuation conductivity depend differently on the tunneling because of their different natures. This study examines the transport in a granular superconductor system in three dimensions in the limit of large tunneling conductance, which makes it possible to ignore all localization effects and the Coulomb interaction. We find that the tunneling is efficient near the critical temperature and that there is a crossover to the characteristic behavior of a homogeneous system. When it is far from the critical temperature, the tunneling is not effective and the system behaves as an ensemble of real zero-dimensional grains. The results show that the Wiedemann-Franz law is violated in both temperature regions.

Key words: granular superconductor, s-wave, impurity vertex, fluctuation propagator

中图分类号:  (Tunneling phenomena; Josephson effects)

  • 74.50.+r
81.05.Rm (Porous materials; granular materials) 47.61.-k (Micro- and nano- scale flow phenomena) 24.60.Ky (Fluctuation phenomena)