Possible pairing states of the Fe-based superconductors

Abstract

We consider the minimal two-band model for the Fe-based superconductors with a phenomenological pairing interaction which mimics short-range antiferromagnetic (AFM) fluctuations. Two superconducting (SC) gap solutions are found to exist with the model: sign-changing s-wave gap ($\pm$s-wave) and double d-wave gap states. Both solutions hold the approximate relation ${\Delta }_h^{max}{N}_h\approx {\Delta }_e^{max}{N}_e$, a generic feature of two band model with a dominant interband pairing interaction. We carried out the calculations of the SC properties of the both SC states such as the density of states, temperature dependencies of spin-lattice relaxation rate $1/T_1$, Knight shift, and penetration depth, particularly taking into account of the interband coherence factors. The results are discussed in comparison with the currently available experimental data.

Published version in Phys. Rev. B 78, 134523 (2008)

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• Microwave Surface-Impedance Measurements of the Magnetic Penetration Depth in Single Crystal Ba1-xKxFe2As2 Superconductors: Evidence for a Disorder-Dependent Superfluid Density
• Superfluid density of the $\pm$s-wave state for the iron-based superconductors
• Origin of Gap Anisotropy in Spin Fluctuation Models of the Fe-pnictides
• Experimental Consequences of the S-wave $\cos (k_x)\cdot \cos (k_y)$ Superconductivity in the Iron-Pnictides
• The London penetration depth in single crystals of Ba(Fe_{1-x}Co_x)_2As_2 at various doping levels
• Interband superconductivity: contrasts between BCS and Eliashberg theory
• Two superconducting gaps in LaFeAsO0.92F0.08 revealed by 75As nuclear quadrupole resonance
• Effects of cobalt doping and three-dimensionality in $BaF{e}_{2}A{s}_2$
• Quantum waveguide theory of Andreev reflection in multiband superconductors: the case of Fe-pnictides
• Systematic ^{75}As NMR study of the dependence of low-lying excitations on F doping in the iron oxypnictide LaFeAs(O_{1-x}F_{x})
• Penetration depth, lower critical fields, and quasiparticle conductivity in Fe-arsenide superconductors
• Surface Bound States in n-band Systems with Quasiclassical Approach
• Isotope effect and the role of phonon in the Fe-based superconductors
• Intergrain Josephson Currents in Multigap Superconductors: Microscopic Origin of Low Intergrain Critical Current and Its Recovery Potential in Iron-Pnictide Materials