Superlattice films of bismuth-based oxide superconductors: change in hole concentration by stress derived from the epitaxial growth

Abstract

Superlattice films of bismuth-based oxide superconductors, such as Bi 2Sr 2Ca 3Cu 4O 12/Bi 2Sr 2Ca 1Cu 2O 8 and Bi 2Sr 2Ca 4Cu 5O 14/Bi 2Sr 2CuO 6, have been synthesized. It was observed that the superconducting transition temperatures were enhanced by forming superlattice films of overdoped ( Bi 2 Sr 2 Ca 1 Cu 2 O 8, Bi 2 Sr 2 CuO 6 ) and underdoped ( Bi 2 Sr 2 Ca 3 Cu 4 O 12, Bi 2 Sr 2 Ca 4 Cu 5 O 14 ) phases. The results can be understood by stress-induced changes in the hole concentration between the over- and the underdoped phases derived from the epitaxial formation of the superlattice films.