David P. Norton

Properties of epitaxial YBa2Cu3O7−δ‐based superconducting superlattices

Epitaxial YBa2Cu3O7−δ‐based superconducting superlattices have been fabricated using pulsed laser deposition in which c‐axis oriented YBa2Cu3O7−δ layers as thin as one unit cell thick are separated by relatively thick PrBa2Cu3O7−δ‐based barrier layers. The superlattice Tc (R=0) decreases rapidly with increasing barrier layer thickness, but then saturates at a finite Tc for YBa2Cu3O7−δ layers as thin as a single c‐axis unit cell The superconducting properties of YBa2Cu3O7−δ‐based superlattices are shown to depend strongly on the electronic properties of the barrier layers. The resistive transition width decreases significantly as the hole carrier density in the barrier layers is increased. However, Tc (onset) does not change, contrary to predictions of hole filling models. Theoretical analyses suggest that the broadening of the resistive transition for the thinnest YBa2Cu3O7−δ layers is most likely due to a crossover to 2D resistive behavior involving thermally‐generated vortices. Scanning tunneling micros...