Exchange-induced ordinary reflection in a single-channel superconductor-ferromagnet-superconductor junction

[摘要] The stationnary Josephson effect in a clean superconductor-ferromagnet-superconductor (SFS) junction is reexamined for arbitrarily large spin polarizations. The quasiclassical calculation of the supercurrent assumes that the Andreev reflection is complete for all channels. However, de Jong and Beenakker have shown that the Andreev reflection at a clean FS interface is incomplete, due to the exchange interaction in the ferromagnet. Taking into account this incomplete Andreev reflection, we investigate the quasiparticle spectrum, the Josephson current and the 0-pi transition in a ballistic single channel SFS junction. We find that energy gaps open in the phase-dependent spectrum. Although the spectrum is strongly modified when the exchange energy increases, the Josephson current and the 0-pi transition are only weakly affected by the incomplete Andreev reflection, except when the exchange energy is close to the Fermi energy.

[发布日期] 2004-12-01

[关键词] SPIN POLARIZATION;ANDREEV REFLECTION;POINT-CONTACT;METAL;TRANSPORT;STATE