Unconventional pairing originating from disconnected Fermi surfaces in the iron-based superconductor

Abstract

For the iron-based high $T_c$ superconductor LaFeAsO${}_{1-x}$F${}_x$, we construct a minimal model, where all of the five Fe $d$ bands turn out to be involved. We then investigate the origin of superconductivity with a five-band random-phase approximation by solving the Eliashberg equation. We conclude that the spin fluctuation modes arising from the nesting between the disconnected Fermi pockets realise, basically, an extended s-wave pairing, where the gap changes sign across the nesting vector.

17pages, 4 figures, to be published in Physica C, Special Edition on Superconducting Pnictides, contains corrections to our previous paper PRL 101, 087004 (2008)

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• Two types of s-wave pairing due to magnetic and orbital fluctuations in the two-dimensional 16-band d-p model for iron-based superconductors
• Surface terminations and layer-resolved spectroscopy in 122 iron pnictide superconductors
• Cooperative effects of Coulomb and electron-phonon interactions in the two-dimensional 16-band d-p model for iron-based superconductors
• Array of Josephson junctions with a non-sinusoidal current-phase relation as a model of the resistive transition of unconventional superconductors
• Influence of multiorbitals and anisotropic Coulomb interactions on isotope effect coefficient in doped Fe-based superconductors
• Orbital driven two-dome superconducting phases in multiorbital superconductors