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

High-Tc superconductors in the two-dimensional limit:

The free modulation of interlayer distance in a layered high-transition temperature (high-Tc) superconductor is of crucial importance not only for the study of the superconducting mechanism but also for the practical application of high-Tc superconducting materials. Two-dimensional (2D) superconductors were achieved by intercalating a long-chain organic compound into bismuth-based high-Tc cuprates. Although the intercalation of the organic chain increased the interlayer distance remarkably, to tens of angstroms, the superconducting transition temperature of the intercalate was nearly the same as that of the pristine material, suggesting the 2D nature of the high-Tc superconductivity.

Tuning High- T c Superconductors via Multistage Intercalation

Multistage intercalation has been used to tune the interaction between adjacent blocks of CuO(2) sheets in the bigh-T(c) (high superconducting transition temperature) superconductor Bi(2)Sr(2)CaCu(2)Ox. As revealed by atomic-resolution transmission electron microscopy images, foreign iodine atoms are intercalated into every nth BiO bilayer of the host crystal, resulting in structures of stoichiometry IBi2nSr2nCanCu2nOx with stage index n up to 4. An expansion of 3.6 angstroms for each intercalated BiO bilayer decouples the CuO(2) sheets in adjacent blocks. A comparison of the superconducting transition temperatures of the pristine host material and intercalated compounds of different stages suggests that the coupling between each pair of adjacent blocks contributes approximately 5 K to T(c) in Bi(2)Sr(2)CaCu(2)Ox.