First-principles calculations for anisotropy of iron-based superconductors

Nakamura, Hiroki  ; Machida, Masahiko  ; Koyama, Tomio*; Hamada, Noriaki*

We perform first-principles calculations for anisotropy of various iron-based superconductors. The anisotropy ratio of the -axis penetration depth to the -plane one is relatively small in BaFeAs, 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 SrScFePO we find a very large value, 200, comparable to that in strongly anisotropic high- cuprate BiSrCaCuO. Thus, the intrinsic Josephson junction stacks are expected to be formed along the -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.