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首页> 美国政府科技报告 >Superconducting properties and microstructure of YBa2Cu3O(7-delta)/PrBa2Cu3O(7-delta) superlattices
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Superconducting properties and microstructure of YBa2Cu3O(7-delta)/PrBa2Cu3O(7-delta) superlattices

机译：YBa2Cu3O（7-delta）/ prBa2Cu3O（7-delta）超晶格的超导特性和微观结构

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Epitaxial YBa(sub 2)Cu(sub 3)O(sub 7-(delta))/PrBa(sub 2)Cu(sub 3)O(sub 7-(delta)) (YBCO/PBCO) superlattices are tools for systematic, fundamental studies of high-temperature superconductivity. The variation of (Tc) in YBCO/PBCO superlattices can be understood as arising from changes in the interlayer phase coupling between YBCO layers that are highly two-dimensional when they are very thin ((approximately)1--2 c-axis unit cells) and completely isolated from each other. Single-cell-thick YBCO layers, containing isolated pairs of CuO(sub 2) planes, are found to be superconducting at (Tc) (approximately) 20 K, in a PBCO matrix. The resistance in the superconducting transition region scales with temperature as expected for the (flux flow) resistance produced by thermally generated 2D vortices, or for a 2D array of superconducting weak links. Relative to both thin-film and single-crystal HTSc specimens, the thin superconducting layers in YBCO/PBCO superlattices exhibit a greatly expanded temperature range over which characteristic 2D dissipation can be observed, as a consequence of the enhanced anisotropy and reduced dimensionality of the YBCO layers. Scanning tunneling microscope studies reveal that YBCO films and YBCO/PBCO superlattices grow unit cell-by-unit cell by a terraced-island growth mechanism. On miscut, near-(001) substrates the terraces are epitaxially aligned with the substrate crystal lattice and spiral growth structures (screw dislocation-mediated growth) are not seen. These observations explain the steps or ''kinks'' that are seen in cross-section Z-contrast TEM images of YBCO/PBCO superlattices. The kinks may correspond physically to regions where the supercurrent must tunnel along the c- axis, and thus may be weak-link barriers. 31 refs., 7 figs.

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