Paraconductivity at high reduced temperatures inYBa2Cu3O7

Abstract

By using high quality single crystals and epitaxial thin films, the in-plane paraconductivity in almost optimally doped YBa 2 Cu 3 O 7Ϫ␦ , with T c0 տ92 K, was determined well inside the so-called short-wavelength fluctuation regime, which corresponds to reduced temperatures, ⑀ϵln(T/T c0 ), above typically ⑀ϭ0.1. It is then shown that these data may be explained in terms of the Gaussian-Ginzburg-Landau approach for bilayered superconductors by introducing a total energy cutoff, instead of the momentum cutoff approximation always used until now. These results seem to confirm the absence of appreciable pseudogap effects on the in-plane resistivity in optimally doped YBa 2 Cu 3 O 7Ϫ␦ superconductors.

Critical fluctuation conductivity in layered superconductors in a strong electric field

“…A formally identical expression was also inferred by Carballeira et al, 35 for Gaussian fluctuations (i.e. with ε = ε), in order to fit the HTSC paraconductivity in the high reduced-temperature region.…”

“…Also a total energy cut-off was suggested, 33,34,35 which eliminates the most energetic fluctuations and not only those with short wavelengths,…”

Critical fluctuations and pseudogap observed in the microwave conductivity ofBi2Sr2CaCuPeligrad1, Mehring2, Dulčić3 2004Phys. Rev. B122100View full textAdd to dashboardCite

“…However, it has been shown recently that energy cutoff should also be imposed in order to satisfy the uncertainty principle for the minimum wave packet of the Cooper pairs 17,18 . For the anisotropic 3D case one should have the condition…”

“…More recent measurements of thermal expansivity 8,9 and two-coil inductive measurements 10 have confirmed this wide range of critical fluctuations, while dc fluctuatuation conductivity measurements still claimed very narrow critical regions 11,12,13,14,15,16 . A major problem in the analysis of a dc fluctuation conductivity is to account for the short wavelength cutoff, 5,6,11,15 and energy cutoff 17,18 at higher temperatures. These effects are so strong that other inherent properties of the fluctuation conductivity can be obscured.…”

Fluctuation conductivity in Y–Ba–Cu–O films with artificially produced defects

“…Measurements taken with a wide variety of techniques demonstrate that the pseudogap is present in both the spin and charge channel but theoretical views of the problem are still rather controversial. One point of view which stands out in the context of experimental evidence is the idea of preformed pairs [1] considered to be the fluctuating Cooper pairs which are believed to be present in HTSC well above T c [2,3]. As structural defects are known to deeply affect the pair-breaking mechanism in high-T c oxides [2], investigation of the influence of systematically produced structural defects on the fluctuation conductivity is to clarify the issue.…”