Abstract
We present a two-fluid description for iron-based superconductors, which contains an itinerant electron Fermi-liquid and a local moment spin-liquid, coupled together via an effective Hund's rule interaction. We examine the low-energy collective behavior of such a system. We find that an electron–spinon composite mode emerges in the intermediate coupling regime, which may account for the hump-dip behavior observed in the recent scanning tunneling spectroscopy experiments. The superconductivity and spin-density-wave phases are consistently described within the same framework. Possible experimental tests are also proposed.
Highlights
The discovery of iron-based superconductors[1] has triggered a new round of intensive research of hightemperature superconductivity
Based on the experimental evidences,[17,18] several versions of the itinerant electrons and local moments hybrid theory were proposed by the authors of Ref. 19–21, and its rich phase diagram was studied in Ref. 22
The iron-based SC is understood as the pairing of itinerant electrons glued by themagnon of local moments, while the spin-densitywave (SDW) order in the parent compounds is considered as a joint ordering of both degrees of freedom whose ordering tendencies are mutually enhanced by the Hund’s rule coupling
Summary
The discovery of iron-based superconductors[1] has triggered a new round of intensive research of hightemperature superconductivity. Motivated by the recent experimental discovery of the gap-like hump-dip feature in the normal phase,[23,24] we conjecture that the local moments may be effectively described by a bosonic spinliquid state, with gapped deconfined spinons, which is important for a consistent explanation (to be discussed in the following) of the observed hump-dip feature. Based on this assumption, we develope a two-fluid description for iron-based superconductors, which contains two liquid components: the itinerant electron Fermiliquid and the local moment spin-liquid.
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