High critical current densities in ultrathin YBa2Cu3O7−δ films sandwiched between (Pr<i>x</i>Y1−<i>x</i>)Ba2Cu3O7−δ layers

Abstract

YBa2Cu3O7−δ (YBCO) films with nominal thicknesses of 1–4 unit cells were grown by pulsed laser deposition using (PrxY1−x)Ba2Cu3O7−δ [(PrxY1−x)BCO] (1≥x≥0) as buffer layers and cap layers. The films of 1 unit cell thick were superconducting for all the x values while Tc increased when x was reduced. For adjacent layers of (Pr0.6Y0.4)BCO which is semiconducting, a Tc of 43 K and Jc of 2×106 A/cm2 for B∥ab and 4×105 A/cm2 for B⊥ab at B=7 T and 4.2 K were obtained in a one-unit cell thick YBCO layer. The Jc values of a few unit cell thick YBCO layers nearly approached that of thick YBCO films. The results suggest the absence of significant weak-link effects in these films.