First-principles calculations for anisotropy of iron-based superconductors

We perform first-principles calculations for anisotropy of various iron-based superconductors. The anisotropy ratio γλ of the c-axis penetration depth to the ab-plane one is relatively small in BaFe2As2, LiFeAs and FeSe, indicating that the transport applications are promising in these superconductors. On the other hand, in those having perovskite-type blocking layers such as Sr2ScFePO3 we find a very large value, γλ ≳ 200, comparable to that in strongly anisotropic high-Tc cuprate Bi2Sr2CaCu2O8−δ. Thus, the intrinsic Josephson junction stacks are expected to be formed along the c-axis, and novel Josephson effects due to the multi-gap nature are also suggested in these superconductors. We also examine the doping effect on the anisotropy of LaFeAsO.