SUPERCONDUCTIVITY IN NONSYMMETRIC EPITAXIAL YBA2CU3O7-X/PRBA2CU3O7-X SUPERLATTICES - THE SUPERCONDUCTING BEHAVIOR OF CU-O BILAYERS

We have fabricated epitaxial, nonsymmetric M×N superlattices in which YBa2Cu3O7-x (YBCO) layers either M=1, 2, 3, 4, or 8 c-axis unit cells thick are separated by insulating PrBa2Cu3O7-x (PrBCO) layers N unit cells thick (N=1 to 16). The zero-resistance transition temperature, Tc0, initially decreases rapidly with increasing PrBCO thickness but saturates at Tc019 K or Tc054 K for 1- and 2-cell-thick YBCO layers, respectively. We conclude that although intercell coupling may enhance Tc0, it is necessary for superconductivity of single-cell-thick YBCO layers in PrBCO matrix. © 1990 The American Physical Society.