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

Abstract

We have successfully intercalated epitaxial iodine spacers between BiO bilayers of the oxide superconductors ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CuO}}_{\mathit{x}}$ (Bi 2:2:0:1), ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{CaCu}}_{2}$${\mathrm{O}}_{\mathit{x}}$ (Bi 2:2:1:2), and ${\mathrm{Bi}}_{2}$${\mathrm{Sr}}_{2}$${\mathrm{Ca}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{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 \AA{} for all three compounds, the materials remain bulk superconductors with transition temperatures ${\mathit{T}}_{\mathit{c}}$ as high as 100 K. The respective shifts in ${\mathit{T}}_{\mathit{c}}$ upon intercalation of the different materials allow examination of the superconductivity mechanism in terms of the role of interplanar and intraplanar Cu-O coupling.