Spin Fluctuations, Interband Coupling, and Unconventional Pairing in Iron-based Superconductors

Abstract

Based on an effective two-band model and using the fluctuation-exchange (FLEX) approach, we explore spin fluctuations and unconventional superconducting pairing in Fe-based layer superconductors. It is elaborated that one type of interband antiferromagnetic (AF) spin fluctuation stems from the interband Coulomb repulsion, while the other type of intraband AF spin fluctuation originates from the intraband Coulomb repulsion. Due to the Fermi-surface topology, a spin-singlet extended s-wave superconducting state is more favorable than the nodal $d_{XY}$-wave state if the interband AF spin fluctuation is more significant than the intraband one, otherwise vice versa. It is also revealed that the effective interband coupling plays an important role in the intraband pairings, which is a distinct feature of the present two-band system.

4 pages, 4 figures, to appear in New Journal of Physics focus issue on iron-based superconductors

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Cited by in corpus (10)

• Coherence-incoherence crossover in the normal state of iron-oxypnictides and importance of the Hund's rule coupling
• Antiferromagnetically Driven Electronic Correlation in Iron Pnictides and Cuprates
• Origin of Gap Anisotropy in Spin Fluctuation Models of the Fe-pnictides
• Effects of cobalt doping and three-dimensionality in $BaF{e}_{2}A{s}_2$
• Tight binding model for iron pnictides
• On interband pairing in multiorbital systems
• Theory of Raman response in a superconductor with extended s-wave symmetry: Application to Fe-pnictides
• Quantum waveguide theory of Andreev reflection in multiband superconductors: the case of Fe-pnictides
• Vortex state in iron-based superconductors with collinear antiferromagnetic cores
• Scanning tunneling microscopy of the 32 K superconductor (Sr1-xKx)Fe2As2