Fluorine-doped structure in iron-based high temperature superconductors

Fluorine-doped iron-based layered LnO1-ΔFΔFeAsLnO1-ΔFΔFeAs with Ln=LaLn=La, Gd, Ce, Pr, Nd, Sm shows a strong correlation between FeF2 positions and the critical transition temperature TcTc. It is suggested that the F-doped Fe2O2 plane serves as the superconducting highway.