First order $0$ - $\pi$ phase transitions in superconductor/ferromagnet/superconductor trilayers

Abstract

We study the thermodynamics of the diffusive SFS trilayer composed of thin superconductor (S) and ferromagnet (F) layers. On the basis the self-consistent solutions of nonlinear Usadel equations in the F and S layers we obtain the Ginzburg--Landau expansion and compute the condensation free energy and entropy of the $0$ (even) and $\pi$ (odd) order parameter configurations. The first order $0-\pi$ transition as a function of temperature $T$ occurs, which is responsible for a jump of the averaged magnetic field penetration depth $\lambda (T)$ recently observed on experiments [N.Pompeo, et. al., Phys. Rev. B 90, 064510 (2014)]. The generalized Ginzburg-Landau functional was proposed to describe SFS trilayer for arbitrary phase difference between the superconducting order parameters in the S layers. The temperature dependence of the SFS Josephson junction critical current demonstrates the strong anharmonicity of the corresponding current--phase relation in the vicinity of the $0-\pi$ transition. In rf SQUID, coexistence of stable and metastable $0$ and $\pi$ states provides integer and half--integer fluxoid configurations.

11 pages, 9 figures

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• Superfluid density of superconductor-ferromagnet bilayers
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Cited by in corpus (8)

• Protected 0-pi states in SIsFS junctions for Josephson memory and logic
• 0-Pi quantum transition in a carbon nanotube Josephson junction: Universal phase dependence and orbital degeneracy
• Temperature controlled FFLO instability in superconductor-ferromagnet hybrids
• Competitive 0 and π states in S/F multilayers: multimode approach
• Phase-dependent Spin Polarization of Cooper Pairs in Magnetic Josephson Junctions
• Robustness of the $0-\pi$ transition against compositional and structural ageing in S/F/S heterostructures
• Long-range triplet proximity effect in multiply connected ferromagnet-superconductor hybrids
• Magnetic field-controlled 0-$\pi$ transitions and their experimental signatures in superconductor-ferromagnet-superconductor junctions