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 $Δ_{h} ^{max} N_h \approx Δ_{e} ^{max} N_e$, 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)