Epitaxial intercalation of the Bi-Sr-Ca-Cu-O superconductor series

We have successfully intercalated epitaxial iodine spacers between BiO bilayers of the oxide superconductors Bi₂{Sr}₂CuOₓ (Bi 2:2:0:1), Bi₂{Sr}₂CaCu₂{O}ₓ$ (Bi 2:2:1:2), and ${Bi}₂Sr₂{Ca}₂Cu₃{O}ₓ$ (Bi 2:2:2:3), thereby forming new c-axis-expanded stage-1 superconducting structures. Although the guest iodine layer expands each BiO bilayer by about 3.6 {} for all three compounds, the materials remain bulk superconductors with transition temperatures Tc as high as 100 K. The respective shifts in Tc upon intercalation of the different materials allow examination of the superconductivity mechanism in terms of the role of interplanar and intraplanar Cu-O coupling.