Josephson current in superconductor-ferromagnet structures with a nonhomogeneous magnetization
By F. Bergeret, A. Volkov, K. Efetov. 2001
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We calculate the dc Josephson current ${I}_{J}$ for two types of superconductor-ferromagnet (S/F) Josephson junctions. The junction of the first type is a S/F/S junction. On the basis of the Eilenberger equation, the Josephson current is calculated for an arbitrary impurity concentration. If $h\ensuremath{\tau}\ensuremath{\ll}1,$ the expression for the Josephson critical current ${I}_{c}$ is reduced to that which can be obtained from the Usadel equation $(h$ is the exchange energy, and \ensuremath{\tau} is the momentum relaxation time). In the opposite limit $h\ensuremath{\tau}\ensuremath{\gg}1$ the superconducting condensate oscillates with period ${v}_{F}/h$ and penetrates into the F region over distances of the order of the mean free path l. For this kind of junctions we also calculate ${I}_{J}$ in the case when the F layer presents a nonhomogeneous (spiral) magnetic structure with the period $2\ensuremath{\pi}/Q.$ It is shown that for not too low temperatures, the \ensuremath{\pi} state which occurs in the case of a homogeneous magnetization $(Q=0)$ may disappear even at small values of Q. In this nonhomogeneous case, the superconducting condensate has a nonzero triplet component and can penetrate into the F layer over a long distance of the order of ${\ensuremath{\xi}}_{T}=\sqrt{D/2\ensuremath{\pi}T}.$ The junction of the second type consists of two S/F bilayers separated by a thin insulating film. It is shown that the critical Josephson current ${I}_{c}$ depends on the relative orientation of the effective exchange field h of the bilayers. In the case of an antiparallel orientation, ${I}_{c}$ increases with increasing h. We establish also that in the F film deposited on a superconductor, the Meissner current created by the internal magnetic field may be both diamagnetic or paramagnetic.
Subfields: Condensed Matter Physics, Electronic, Optical and Magnetic Materials
View Paper: https://www.semanticscholar.org/paper/fed4aa82351fc09ba6b1aa5216cd86880ab4d114
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In Electronic, Optical and Magnetic Materials
Citations in the corpus
- Odd-frequency superconductivity (2017, background): “The approach by Bergeret et al.was different from previous literature in that they had focused on the possibility of having odd-ω pairing in the bulk of a material instead of arising as a proximity effect.”
- Odd triplet superconductivity and related phenomena in superconductor-ferromagnet structures (2005, background): “Here γ = ρξh/Rb. ∆/ET ≫ 1 and w/L = 0.05 (from Bergeret, Volkov, and Efetov (2001a)).”