Critical Temperature Oscillations and Reentrant Superconductivity due to the FFLO like State in F/S/F Trilayers

TL;DR

This paper investigates how FFLO-like states in F/S/F trilayers cause critical temperature oscillations and reentrant superconductivity, which are crucial for enhancing superconducting spin valve effects, demonstrated experimentally in CuNi/Nb/CuNi structures.

Contribution

The study provides experimental evidence of strong critical temperature oscillations and reentrant superconductivity due to FFLO-like states in F/S/F trilayers, advancing understanding of superconducting spin valves.

Findings

Observation of critical temperature oscillations as a function of ferromagnetic layer thickness.

Demonstration of reentrant superconductivity in CuNi/Nb/CuNi trilayers.

Experimental validation of FFLO-like state effects in F/S/F structures.

Abstract

Ferromagnet/Superconductor/Ferromagnet (F/S/F) trilayers, in which the establishing of a Fulde-Ferrell Larkin-Ovchinnikov (FFLO) like state leads to interference effects of the superconducting pairing wave function, form the core of the superconducting spin valve. The realization of strong critical temperature oscillations in such trilayers, as a function of the ferromagnetic layer thicknesses or, even more efficient, reentrant superconductivity, are the key condition to obtain a large spin valve effect, i.e. a large shift in the critical temperature. Both phenomena have been realized experimentally in the Cu 41 Ni 59 /Nb/Cu 41 Ni 59 trilayers investigated in the present work.