First-Principles Study for the Anisotropy of Iron-Based Superconductors toward Power and Device Applications

Performing the first-principles calculations, we investigate the anisotropy in the superconducting state of iron-based Superconductors to gain an insight into their potential applications. The anisotropy ratio gamma(lambda) of the c-axis penetration depth to the ab-plane one is relatively small in BaFe2As2 and LiFeAs, i.e., gamma(lambda) similar to 3, 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, gamma(lambda) greater than or similar to 200, comparable to that in strongly anisotropic high-T-c cuprate Bi2Sr2CaCu2O8-delta. 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.