Hund interaction, spin-orbit coupling and the mechanism of superconductivity in strongly hole-doped iron pnictides

Abstract

We present a novel mechanism of s-wave pairing in Fe-based superconductors. The mechanism involves holes near dxz/dyz pockets only and is applicable primarily to strongly hole doped materials. We argue that as long as the renormalized Hund's coupling J exceeds the renormalized inter-orbital Hubbard repulsion U', any finite spin-orbit coupling gives rise to s-wave superconductivity. This holds even at weak coupling and regardless of the strength of the intra-orbital Hubbard repulsion U. The transition temperature grows as the hole density decreases. The pairing gaps are four-fold symmetric, but anisotropic, with the possibility of eight accidental nodes along the larger pocket. The resulting state is consistent with the experiments on KFe2As2.

5 pages (main text) + 5 pages (supplementary material), 3 figures

References in corpus (9)

• High-temperature superconductivity in iron-based materials
• Strong electronic correlations from Hund's coupling
• Near-degeneracy of several pairing channels in multiorbital models for the Fe-pnictides
• Coherence-incoherence crossover in the normal state of iron-oxypnictides and importance of the Hund's rule coupling
• Spin-triplet p-wave pairing in a 3-orbital model for iron pnictide superconductors
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• Collective modes in multiband superconductors: Raman scattering in iron selenides
• Electronic structure and de Haas-van Alphen frequencies in KFe2As2 within LDA+DMFT
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