Superconductivity in a Two-Orbital Hubbard Model with Electron and Hole Fermi Pockets: Application in Iron Oxypnictide Superconductors

Abstract

We investigate the electronic states of a one-dimensional two-orbital Hubbard model with band splitting by the exact diagonalization method. The Luttinger liquid parameter $K_{\rho }$ is calculated to obtain superconducting (SC) phase diagram as a function of on-site interactions: the intra- and inter-orbital Coulomb $U$ and $U^{\prime }$, the Hund coupling $J$, and the pair transfer $J^{\prime }$. In this model, electron and hole Fermi pockets are produced when the Fermi level crosses both the upper and lower orbital bands. We find that the system shows two types of SC phases, the SC \Roman{u'-large} for $U>U^{\prime }$ and the SC \Roman{u-large} for $U<U^{\prime }$, in the wide parameter region including both weak and strong correlation regimes. Pairing correlation functions indicate that the most dominant pairing for the SC \Roman{u'-large} (SC \Roman{u-large}) is the intersite (on-site) intraorbital spin-singlet with (without) sign reversal of the order parameters between two Fermi pockets. The result of the SC \Roman{u'-large} is consistent with the sign-reversing s-wave pairing that has recently been proposed for iron oxypnictide superconductors.

5 pages, 8 figures, to appear in J. Phys. Soc. Jpn., Vol.78, No.12, p.124706

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Cited by in corpus (7)

• 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
• Orbital Order, Structural Transition and Superconductivity in Iron Pnictides
• Potential antiferromagnetic fluctuations in hole-doped iron-pnictide superconductor Ba_{1-x}K_{x}Fe_{2}As_{2} studied by ^{75}As nuclear magnetic
• Pairing Tendencies in a Two-orbital Hubbard Model in One Dimension
• Cooperative effects of Coulomb and electron-phonon interactions in the two-dimensional 16-band d-p model for iron-based superconductors
• Excitonic Order and Superconductivity in the Two-Orbital Hubbard Model: Variational Cluster Approach
• Particular type of gap in the spectrum of multiband superconductors