First-principles study for the anisotropy of iron-based superconductors toward power and device applications

電力・デバイス応用に向けた鉄系超伝導体の異方性に関する第一原理計算による研究

中村 博樹  ; 町田 昌彦  ; 小山 富男*; 浜田 典昭*

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

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 of the -axis penetration depth to the -plane one is relatively small in BaFeAs and LiFeAs, i.e., , 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, , 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.