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arXiv · 1408.0665

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

N. Pompeo·K. Torokhtii·C. Cirillo·A. V. Samokhvalov·E. A. Ilyina·C. Attanasio·A. I. Buzdin·E. Silva
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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.

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N. Pompeo, K. Torokhtii, C. Cirillo, A. V. Samokhvalov, E. A. Ilyina, C. Attanasio, A. I. Buzdin, E. Silva. 2014-08-04. Thermodynamic nature of the 0-PI quantum transition in superconductor-ferromagnet-superconductor trilayers. https://doi.org/10.1103/physrevb.90.064510

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