Tuning High- <i>T</i> _c Superconductors via Multistage Intercalation

Abstract

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.