Superconductivity and interlayer coupling in ultrathin artificially layered cuprates

A structural requirement for high-T(c) (FITS) cuprates is the simultaneous presence in a layered structure of two different functional blocks, individually non-superconducting: the charge reservoir (CR) block and the infinite layer (IL) block. Artificially layered 2 x m superlattices were grown, by pulsed laser deposition, stacking epitaxially m layers of (Ba(0.9)Nd(0.1))CuO(2+delta) and two layers of CaCuO(2). Starting from superlattices with m = 2, the thickness of CR block, namely the Ba-Cu-O block. which separates adjacent Ca-Cu-O IL blocks. was gradually increased up to m = 10. In the superlattices with m > 4 the superconducting layers are completely decoupled. showing. relative to the m = 2 superlattice. a negligible decrease of the transition temperature and a strong increase of the anisotropy. Superconductivity at 55 K was found in both the ultrathin films, only consisting of two CR blocks sandwiching a (CaCUO(2))(2) layer, and the superlattices with thick CR blocks. demonstrating that the interlayer coupling in Such heterostructures is unimportant. Moreover it has been shown that a single CaCuO(2) layer is still superconducting.