Superconducting superlattices: Verification of two-dimensional nature in high Tc Bi2Sr2(Ca1 - xYx)Cu2O8 superconductors

An approach to evaluate the two-dimensional nature in a high T_c superconductor is examined on the superconducting superlattice prepared by stacking of superconductor and nonsuperconductor layers. The Bi₂Sr₂(Ca_1-xY_x)₁Cu₂O₈-based superlattices have been formed by stacking two different unit cell layers containing different yttrium concentrations. One unit layer contains lower yttrium concentration (x=0.15) to be a superconductor, and the other contains higher concentration (x=0.5) to be a semiconductor, and these layers are periodically stacked with appropriate ratios. These superlattices exhibit the same resistance-temperature curve as the original superconducting films with x=0.15. This behavior can be explained by the strong two-dimensional character in this Bi₂Sr₂(Ca_1-xY_x)Cu₂O₈ high T_c superconductor.