On the Coexistence of Superconductivity and Magnetic Ordering in Unconventional Superconductors
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It is demonstrated that the coexistence of superconductivity and magnetic ordering, occurring, for instance, in iron-based pnictides and uranium compounds, is not forbidden by classical Maxwell’s equations and London-type equations. It predicts simply that internal magnetization is allowed but localized magnetic moments are screened at distances of the order of the London penetration depth. A microscopic theory is considered for the case of ferromagnetic ordering, described in simple terms by electron-magnon coupling. For the sake of simplicity, we assume that itinerant electrons are not responsible for the magnetic ordering, but interact with phonon and magnon excitations, leading to an alternative Cooper pair channel. The temperature dependence and the isotope effect of the superconducting gap is also analysed.
KeywordsIron-based superconductors London equations Unconventional superconductivity BCS theory
C.A. Dartora would like to thank the Brazilian agency CNPq for partial financial support through grant and scholarship CNPq 471521/2013-2 and 301894/2014-0.
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