Critical Temperature and Isotope Exponent in a Two-band Model for Superconducting Fe-pnictides

Rodríguez-Núñez, J. J.; Schmidt, Ann; Citro, Roberta; Noce, Canio

doi:10.1007/s10948-009-0466-9

Cited by 3 publications

(1 citation statement)

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“…24-26, 28, 29 Here, we employ the two orbital Hubbard model 30 reproducing the electron and hole FSs as a minimal model for ironbased superconductors. The model has been extensively studied by many authors focusing on the pairing states, ?, [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] magnetic states, [47][48][49][50][51][52][53][54][55][56][57][58][59][60] strong correlation effects [61][62][63][64] and lattice and orbital properties. [65][66][67] However, the effect of the JT phonon, which has been found to play important role in the orbital fluctuations responsible for the softening of C 66 , 10,11 was not discussed there.…”

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confidence: 99%

Metal–Insulator Transition and Superconductivity in the Two-Orbital Hubbard–Holstein Model for Iron-Based Superconductors

2014

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We investigate a two-orbital model for iron-based superconductors to elucidate the effect of interplay between electron correlation and Jahn-Teller electron-phonon coupling by using the dynamical mean-field theory combined with the exact diagonalization method. When the intra-and inter-orbital Coulomb interactions, U and U ′ , increase with U = U ′ , both the local spin and orbital susceptibilities, χ s and χ o , increase with χ s = χ o in the absence of the Hund's rule coupling J and the electron-phonon coupling g. In the presence of J and g, there are distinct two regimes: for J > ∼ 2g 2 /ω 0 with the phonon frequency ω 0 , χ s is enhanced relative to χ o and shows a divergence at J = J c above which the system becomes Mott insulator, while for J < ∼ 2g 2 /ω 0 , χ o is enhanced relative to χ s and shows a divergence at g = g c above which the system becomes bipolaronic insulator. In the former regime, the superconductivity is mediated by antiferromagnetic fluctuations enhanced due to Fermi-surface nesting and is found to be largely dependent on carrier doping. On the other hand, in the latter regime, the superconductivity is mediated by ferro-orbital fluctuations and is observed for wide doping region including heavily doped case without the Fermi-surface nesting.

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