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Temperature induced transition of thin superconductor-ferromagnet-normal (S/F/N) metal hybrid structure to in-plane Fulde-Ferrel-Larkin-Ovchinnikov (FFLO) state is accompanied by vanishing of effective inverse magnetic field penetration depth Λ −1 (Phys. Rev. Lett. 121, 077002 (2018)).Here we show that Λ −1 goes to zero only in limit of zero magnetic field H → 0 and at any finite parallel H or in-plane current I it is finite and positive in FFLO state which implies diamagnetic response. We demonstrate that Λ −1 has a nonmonotonic dependence on H and I not only in the parameter range corresponding to the FFLO phase domain but also in its vicinity. We find that for S/F/N/F/S structures with certain thicknesses of F layers there is temperature, current and magnetic field driven transition to and out of FFLO phase with a simultaneous jump of Λ −1

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We calculate the current–phase relation (CPR) of a SN-S-SN Josephson junction based on a SN bilayer of variable thickness composed of a highly disordered superconductor (S) and a low-resistivity normal metal (N) with proximity-induced superconductivity. In such a junction, the N layer provides both a large concentration of phase in the weak link and good heat dissipation. We find that when the thickness of the S and the N layer and the length of the S constriction are about the superconducting coherence length the CPR is single-valued and can be close to a sinusoidal shape. The product I c R n can reach Δ(0)/2|e| (I c is the critical current of the junction, R n is its normal-state resistance, Δ(0) is the superconductor gap of a single S layer at zero temperature). Our calculations show, that the proper choice of the thickness of the N layer leads both to nonhysteretic current–voltage characteristics even at low temperatures and a relatively large product I c R n.

Using time-dependent Ginzburg-Landau theory we find oscillations of critical current density jc as a function of the length L of the bridge formed from two-band superconductor. We explain this effect by appearance of the phase solitons in the bridge at j < jc, those number changes with change of L. In case of sufficiently strong interband coupling oscillations of jc disappear.