We consider a long diffusive Josephson junction where the weak link is a thin (normal metal (N)–ferromagnet (F)) bilayer (N and F form parallel links between superconductors (Ss)). We show that superconductivity in the weak link can be described by an effective one-dimensional Usadel equation containing a “diluted” exchange field as well as a weak depairing term that is caused by the inherent inhomogeneity of the bilayer. The depairing mechanism distinguishes the S(N/F)S system from an SFS junction and affects the density of states of the S(N/F)S junction. It results in the suppression of the minigap in the spin-resolved density of states. The depairing rate and the minigap are expressed in terms of geometrical parameters, the Thouless energy and the effective exchange field. The effective one-dimensional theory can be applied to various structures with thin inhomogeneous links and shows good agreement with numerical solutions of the original two-dimensional equations. We also discuss ways to reveal the predicted effect experimentally.
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ACKNOWLEDGMENTS
We thank V.V. Ryazanov, Ya.V. Fominov, P.M. Ostrovsky, and M.V. Feigel’man for valuable discussions.
Funding
This work was supported by the Russian Science Foundation (project no. 19-72-00125). Numerical studies of the one-dimensional Usadel equation were supported by the Higher School of Economics (basic research program).
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Ioselevich, P.A., Chuklanov, D.A. Minigap Suppression in S(N/F)S Junctions. Jetp Lett. 113, 631–637 (2021). https://doi.org/10.1134/S0021364021100027
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DOI: https://doi.org/10.1134/S0021364021100027