Coexistence of itinerant electrons and local moments in iron-based superconductorsSu-Peng Kou1, Tao Li2 and Zheng-Yu Weng3
1 Department of Physics, Beijing Normal University - Beijing, 100875, China
2 Department of Physics, Renmin University of China - Beijing, 100872, China
3 Center for Advanced Study, Tsinghua University - Beijing, 100084, China
received 24 April 2009; accepted in final form 16 September 2009; published October 2009
published online 23 October 2009
In view of the recent experimental facts in the iron-pnictides, we make a proposal that the itinerant electrons and local moments are simultaneously present in such multiband materials. We study a minimal model composed of coupled itinerant electrons and local moments to illustrate how a consistent explanation of the experimental measurements can be obtained in the leading-order approximation. In this mean-field approach, the spin-density-wave (SDW) order and superconducting pairing of the itinerant electrons are not directly driven by the Fermi surface nesting, but are mainly induced by their coupling to the local moments with momentum match. The presence of the local moments as independent degrees of freedom naturally provides strong pairing strength for superconductivity and also explains the normal-state linear-temperature magnetic susceptibility above the SDW transition temperature. We show that this simple model is supported by various anomalous magnetic properties which are in quantitative agreement with experiments.
74.20.Mn - Nonconventional mechanisms (spin fluctuations, polarons and bipolarons, resonating valence bond model, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.).
71.27.+a - Strongly correlated electron systems; heavy fermions.
75.20.Hr - Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions.
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