S Graser et al 2009 New J. Phys. 11 025016 doi:10.1088/1367-2630/11/2/025016
Near-degeneracy of several pairing channels in multiorbital models for the Fe pnictides
Focus on Iron-Based SuperconductorsS Graser1,4, T A Maier2, P J Hirschfeld1 and D J Scalapino3
Show affiliationsPart of Focus on Iron-Based Superconductors
Weak-coupling approaches to the pairing problem in the iron pnictide superconductors have predicted a wide variety of superconducting ground states. We argue here that this is due both to the inadequacy of certain approximations to the effective low-energy band structure, and to the natural near degeneracy of different pairing channels in superconductors with many distinct Fermi surface sheets. In particular, we review attempts to construct two-orbital effective band models, the argument for their fundamental inconsistency with the symmetry of these materials, and compare the dynamical susceptibilities of two- and five-orbital tight-binding models. We then present results for the magnetic properties, pairing interactions and pairing instabilities within a five-orbital tight-binding random phase approximation model. We discuss the robustness of these results for different dopings, interaction strengths and variations in band structures. Within the parameter space explored, an anisotropic, sign-changing s-wave (A1g) state and a 
(B1g) state are nearly degenerate, due to the near nesting of Fermi surface sheets.
- PACS
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74.70.Dd Ternary, quaternary and multinary compounds (including Chevrel phases, borocarbides, etc.)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
- Subjects
- Dates
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Issue 2 (February 2009)
Received 28 November 2008
Published 27 February 2009
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Near-degeneracy of several pairing channels in multiorbital models for the Fe pnictides
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