Extended Hubbard model of superconductivity driven by charge fluctuations in iron-pnictides

Abstract

We present a scenario for iron-pnictide superconductivity mediated by charge fluctuations that are strongly enhanced by Fe-As intersite electronic interactions. Deriving an eight-band extended Hubbard model including Fe 3$d$ and As 4$p$ orbitals for the LaOFeAs family, we show that charge fluctuations induced by $p$-$d$ charge transfer and As orbital polarization interactions in the Fe-pnictogen structure peak at wavevectors $(0,0)$, and ($\pi$, 0) and ($\pi$, $\pi$) respectively. Intraorbital spin-singlet pairing attraction develops at these wavevectors and the solution of the linearized gap equation shows robust s-wave superconductivity with both $s_{\pm }$ and $s_{++}$ gap functions.

revised version, to be published in Phys. Rev. B as a rapid communication. 5 pages, 4 eps figures and 1 table

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• ARPES measurements of the superconducting gap of Fe-based superconductors and their implications to the pairing mechanism
• Observation of an isotropic superconducting gap at the Brillouin zone center of Tl${}_{0.63}$K${}_{0.37}$Fe${}_{1.78}$Se${}_2$
• Hubbard-like Hamiltonians for interacting electrons in s, p and d orbitals
• Coexistence of orbital degeneracy lifting and superconductivity in iron-based superconductors
• Charge-Stripe Order in a Parent Compound of Iron-based Superconductors
• Non-local correlations in Iron Pnictides and Chalcogenides
• A High-Tc Mechanism of Iron Pnictide Superconductivity due to Cooperation of Ferro-orbital and Antiferromagnetic Fluctuations
• Nonlocal Coulomb interaction and spin-freezing crossover as a route to valence-skipping charge order
• Orbital selectivity of layer resolved tunneling on iron superconductor Ba0.6K0.4Fe2As2
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• Contrast of LiFeAs with isostructural, isoelectronic, and non-superconducting MgFeGe
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• Intrinsic chiral topological superconductor thin films