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Measurement of the Current-Phase Relation of SFS pi-Josephson junctions

S. M. Frolov·D. J. Van Harlingen·V. A. Oboznov·V. V. Bolginov·V. V. Ryazanov
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Abstract

We present measurements of the current-phase relation (CPR) of Superconductor-Ferromagnet-Superconductor (SFS) Josephson junctions as a function of temperature. The CPR is determined by incorporating the junction into a superconducting loop coupled to a dc SQUID, allowing measurement of the junction phase difference. Junctions fabricated with a thin (~ 22 nm) barrier of Cu0.47Ni0.53 sandwiched between Nb electrodes exhibit a re-entrant critical current with temperature, vanishing at T =T_pi ~ 2-4 K. We find that the critical current is negative for T < T_pi, indicating that the junction is a pi-Josephson junction. We find no evidence for second-order Josephson tunneling near T_pi in the CPR predicted by several theories.

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S. M. Frolov, D. J. Van Harlingen, V. A. Oboznov, V. V. Bolginov, V. V. Ryazanov. 2004-02-17. Measurement of the Current-Phase Relation of SFS pi-Josephson junctions. https://arxiv.org/abs/cond-mat/0402434

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