Impurity-induced in-gap state and Tc in sign-reversing s-wave superconductors: analysis of iron oxypnictide superconductors

Abstract

The sign-reversing fully gapped superconducting state, which is expected to be realized in oxypnictide superconductors, can be prominently affected by nonmagnetic impurities due to the interband scattering of Cooper pairs. We study this problem based on the isotropic two-band BCS model: In oxypnictide superconductors, the interband impurity scattering $I^{\prime }$ is not equal to the intraband one $I$. In the Born scattering regime, the reduction in Tc is sizable and the impurity-induced density of states (DOS) is prominent if $I\sim I^{\prime }$, due to the interband scattering. Although impurity-induced DOS can yield a power-law temperature dependence in $1/T_1$, a sizable suppression in Tc is inevitably accompanied. In the unitary scattering regime, in contrast, impurity effect is very small for both Tc and DOS except at $I=I^{\prime }$. By comparing theory and experiments, we expect that the degree of anisotropy in the $s_{\pm }$-wave gap function strongly depends on compounds.

16 pages, 5 figures, to be published in New. J. Phys

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Cited by in corpus (3)

• Microwave Surface-Impedance Measurements of the Magnetic Penetration Depth in Single Crystal Ba1-xKxFe2As2 Superconductors: Evidence for a Disorder-Dependent Superfluid Density
• Magnetic impurities in the two-band $s_{\pm }$-wave superconductors
• Single Impurity Effects in Multiband Superconductors with Different Sign Order Parameters