Fluctuation-induced diamagnetism at high reduced temperatures in

By using two randomly oriented polycrystalline YBa2Cu3O$_{7-\delta}$ samples with masses as big as $0.63 \rm{g}$ and $0.90 \rm{g}$, but almost optimally doped ($T_{\rm c0} \simeq 90.8 \rm{K}$ and $92.0 \rm{K}$) and with excellent stoichiometric homogeneity, the in-plane fluctuation-induced diamagnetism was determined, for the first time in any superconductor, well inside the so-called short wavelength regime in the zero-magnetic-field limit, which corresponds to reduced temperatures, $\epsilon \equiv \ln (T/T_{\rm c0})$, above typically $\epsilon = 0.1$. It is then shown that these measurements may be explained in terms of the Schmidt limit of the Gaussian-Ginzburg-Landau approach for bilayered superconductors by introducing a total-energy cut-off in the fluctuation spectrum