Theory for Superconductivity in Iron Pnictides at Large Coulomb U Limit
Wei-Qiang Chen, Kai-Yu Yang, Yi Zhou, and Fu-Chun Zhang
TL;DR
This paper develops a theoretical model for superconductivity in iron pnictides, showing how Coulomb interactions influence pairing symmetry and aligning with recent experimental observations.
Contribution
It introduces a two-orbital Hubbard model in the large U limit to explain pairing mechanisms and symmetry transitions in iron pnictides.
Findings
Orbital-dependent pairing induced by Coulomb repulsion.
Superconducting symmetry shifts from extended s-wave to d-wave with increasing Hund's coupling.
Model aligns with ARPES and Andreev reflection experimental results.
Abstract
Superconductivity in iron pnictides is studied by using a two-orbital Hubbard model in the large U limit. The Coulomb repulsion induces an orbital-dependent pairing between charge carriers. The pairing is found mainly from the scattering within the same Fermi pocket. The inter-pocket pair scatterings determine the symmetry of the superconductivity, which is extended s-wave at small Hund's coupling, and d-wave at large Hund's coupling and large U. The former is consistent with recent experiments of ARPES and Andreev reflection spectroscope.
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