Thermodynamic nature of the 0-PI quantum transition in superconductor-ferromagnet-superconductor trilayers

Abstract

In structures made up of alternating superconducting and ferromagnet layers (S/F/S heterostructures), it is known that the macroscopic quantum wavefunction of the ground state changes its phase difference across the F--layer from 0 to PI under certain temperature and geometrical conditions, whence the name "0-PI" for this crossover. We present here a joint experimental and theoretical demonstration that the "0-PI" is a true thermodynamic phase transition: microwave measurements of the temperature dependence of the London penetration depth in Nb/Pd_0.84Ni_0.16/Nb trilayers reveal a sudden, unusual decrease of the density of the superconducting condensate (square modulus of the macroscopic quantum wavefunction) with decreasing temperature, which is predicted by the theory here developed as a transition from the 0- to the PI-state. Our result for the jump of the amplitude of the order parameter is the first thermodynamic manifestation of such temperature-driven quantum transition.

arXiv comment7 pages, 5 figures. Accepted for publication in Phys. Rev. B, http://journals.aps.org/prb/

References in corpus (9)

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• Reliable determination of vortex parameters from measurements of the microwave complex resistivity
• Striking properties of Superconductor/Ferromagnet structures with spin-dependent scattering
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• Wideband microwave measurements in Nb/Pd${}_{84}$Ni${}_{16}$/Nb structures and comparison with thin Nb films
• Superfluid density of superconductor-ferromagnet bilayers
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• Robustness of the $0-\pi$ transition against compositional and structural ageing in S/F/S heterostructures
• First order $0$ - $\pi$ phase transitions in superconductor/ferromagnet/superconductor trilayers
• Pinning properties of FeSeTe thin film through multifrequency measurements of the surface impedance
• Long-range triplet proximity effect in multiply connected ferromagnet-superconductor hybrids
• Abrikosov vortices in SF bilayers