First-order phase transition by a spin-flip potential in BCS superconductivity

•First-order phase transition was observed in conventional superconductors;•The tri-critical point was obtained using statistical physics arguments;•Each point of a first-order frontier can be determined by the Clausius–Clapeyron relation. A spin-flip potential V is added to a BCS Hamiltonian in ord...

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Bibliographic Details
Published in:Physica. C, Superconductivity Superconductivity, 2019-09, Vol.564, p.75-79
Main Authors: Rodriguez Salmon, Octavio D., Dinóla Neto, Francisco, Padilha, Igor Tavares, Adão Neto, Minos M.
Format: Article
Language:English
Subjects:
Energy conservation
Free energy
Ising model
Magnetism
Phase diagrams
Phase transitions
Superconductivity
Superconductors
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Summary:•First-order phase transition was observed in conventional superconductors;•The tri-critical point was obtained using statistical physics arguments;•Each point of a first-order frontier can be determined by the Clausius–Clapeyron relation. A spin-flip potential V is added to a BCS Hamiltonian in order to study its effect on the superconducting phase from a statistical physics point of view. The spin-flip potential could also be understood as a simplified way of representing the effect of impurities in a conventional superconductor. We found that the competition between the pairing and the spin-flip effect gives rise to a first-order phase transition for a range of values of V, before the total destruction of the superconducting order. The phase diagram shows a tricritical point in a frontier line which is topologically similar to those found in the phase diagrams of some Ising-like models as the Blume–Capel model. The first-order frontier was obtained numerically by free energy minimization.
ISSN:0921-4534
1873-2143
DOI:10.1016/j.physc.2019.05.007