In structures made up of alternating superconducting and ferromagnet layers (S/F/S heterostructures), it is known that the macroscopic quantum wave function of the ground state changes its phase difference across the F layer from 0 to π under certain temperature and geometrical conditions, hence the name "0-π" for this crossover. We present here a joint experimental and theoretical demonstration that 0-π is a true thermodynamic phase transition. Microwave measurements of the temperature dependence of the London penetration depth in Nb/Pd0.84Ni0.16/Nb trilayers reveal a sudden, unusual decrease of the density of the superconducting condensate (square modulus of the macroscopic quantum wave function) with decreasing temperature, which is predicted by the theory here developed as a transition from the 0 state to the π state. Our result for the jump of the amplitude of the order parameter is a thermodynamic manifestation of such a temperature-driven quantum transition.

Pompeo, N., Torokhtii, K., Cirillo, C., Samokhvalov, A.V., Ilyina, E.A., Attanasio, C., et al. (2014). Thermodynamic nature of the 0 − π quantum transition in superconductor/ ferromagnet/ superconductor trilayers. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 90(6), 064510 [10.1103/PhysRevB.90.064510].

Thermodynamic nature of the 0 − π quantum transition in superconductor/ ferromagnet/ superconductor trilayers

POMPEO, NICOLA;TOROKHTII, KOSTIANTYN;SILVA, Enrico
2014-01-01

Abstract

In structures made up of alternating superconducting and ferromagnet layers (S/F/S heterostructures), it is known that the macroscopic quantum wave function of the ground state changes its phase difference across the F layer from 0 to π under certain temperature and geometrical conditions, hence the name "0-π" for this crossover. We present here a joint experimental and theoretical demonstration that 0-π is a true thermodynamic phase transition. Microwave measurements of the temperature dependence of the London penetration depth in Nb/Pd0.84Ni0.16/Nb trilayers reveal a sudden, unusual decrease of the density of the superconducting condensate (square modulus of the macroscopic quantum wave function) with decreasing temperature, which is predicted by the theory here developed as a transition from the 0 state to the π state. Our result for the jump of the amplitude of the order parameter is a thermodynamic manifestation of such a temperature-driven quantum transition.
Pompeo, N., Torokhtii, K., Cirillo, C., Samokhvalov, A.V., Ilyina, E.A., Attanasio, C., et al. (2014). Thermodynamic nature of the 0 − π quantum transition in superconductor/ ferromagnet/ superconductor trilayers. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 90(6), 064510 [10.1103/PhysRevB.90.064510].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11590/119698
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