Vortex fluctuations and two-dimensional Coulomb-gas scaling for crystalline ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$/${\mathrm{PrBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ superlattices

An analysis of resistance data for crystalline ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$/${\mathrm{PrBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ superlattices that reveals a new fine structure is presented. This fine structure, which is directly related to the two-dimensional (2D) to three-dimensional crossover close to ${\mathit{T}}_{\mathit{c}}$, gives a measure of the effective anisotropy of the various superlattices. The data is remarkably well explained by the 2D Ginzburg-Landau Coulomb-gas model and the fine structure can be attributed to the coupling between the superconducting ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ layers.