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arXiv · 0809.1470

Sign reversal of ac Josephson current in a ferromagnetic Josephson junction

S. Hikino·M. Mori·S. Takahashi·S. Maekawa
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Abstract

The ac Josephson effect in a ferromagnetic Josephson junction, which is composed of two superconductors separated by a ferromagnetic metal (FM), is studied by a tunneling Hamiltonian and Green's function method. We obtain two types of superconducting phase dependent current, i.e., Josephson current and quasiparticle-pair-interference current (QPIC). These currents change their signs with thickness of the FM layer due to the 0-$π$ transition characteristic to the ferromagnetic Josephson junction. As a function of applied voltage, the Josephson critical current shows a logarithmic divergence called the Riedel peak at the gap voltage, while the QPIC shows a discontinuous jump. The Riedel peak reverses due to the 0-$π$ transition and disappears near the 0-$π$ transition point. The discontinuous jump in the QPIC also represents similar behaviors to the Riedel peak. These results are in contrast to the conventional ones.

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S. Hikino, M. Mori, S. Takahashi, S. Maekawa. 2009-01-15. Sign reversal of ac Josephson current in a ferromagnetic Josephson junction. https://doi.org/10.1143/jpsj.78.014708

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