Odd-frequency pairs and Josephson current through a strong ferromagnet

• Asano, Yasuhiro

• Sawa, Yuki

• Tanaka, Yukio

• Golubov, Alexander A.

Abstract

We study Josephson current in superconductor/diffusive ferromagnet/superconductor junctions by using the recursive Green function method. When the exchange potential in a ferromagnet is sufficiently large compared to the pair potential in a superconductor, an ensemble average of Josephson current is much smaller than its mesoscopic fluctuations. The Josephson current vanishes when the exchange potential is extremely large so that a ferromagnet is half-metallic. Spin-flip scattering at junction interfaces drastically changes the characteristic behavior of Josephson current. In addition to spin-singlet Cooper pairs, equal-spin triplet pairs penetrate into a half metal. Such equal-spin pairs have an unusual symmetry property called odd-frequency symmetry and carry the Josephson current through a half metal. The penetration of odd-frequency pairs into a half metal enhances the low energy quasiparticle density of states, which could be detected experimentally by scanning tunneling spectroscopy. We will also show that odd-frequency pairs in a half metal cause a nonmonotonic temperature dependence of the critical Josephson current.

Journal

• PHYSICAL REVIEW B

  PHYSICAL REVIEW B 76 (22), 224525-224525, 2007-12

  American Physical Society

Keywords

• Cooper pairs
• critical current density (superconductivity)
• electronic density of states
• exchange interactions (electron)
• ferromagnetic materials
• Green's function methods
• interface states
• Josephson effect
• magnetic superconductors
• mesoscopic systems
• quasiparticles
• scanning tunnelling microscopy
• spin fluctuations
• triplet state

Details

• CRID: 1050282813774702464
• NII Article ID: 120001151498
• HANDLE: 2237/11285
• ISSN: 10980121
• Web Site: https://nagoya.repo.nii.ac.jp/records/9503
• Text Lang: en
• Article Type: journal article
• Data Source:
  • IRDB
  • CiNii Articles