Electrical resistivity and magnetic susceptibility roundings above the superconducting transition in Y₁Ba₂Cu₃O_{7- delta}

Abstract

We report high-resolution data of the electrical resistivity and of the magnetic susceptibility rounding effects above the superconducting transition in single-phase polycrystalline YBa,Cu,O,.* compounds. These data may be explained quantitatively and consistently, over two orden of magnitude in reduced temperature, by direct three-dimensional thermodynamic fluctuations of the amplitude of a two-component order parameter in unconventional (non-rwave pairing) superconductors. The resulting order parameter correlationlengthamplitudesareEab(0) = ( U + 3)A,andE,(0) = (1.4 +0.4).&, theLawrence-Doniach effective interlayer distance is d. = (8 3' 2) A, and the Ginzburg reduced temperature is = (0.7 * 0.3) X

The conductivity and the magnetization around Tc in optimally-doped YBa$_2$Cu$_3$O$_{7-δ}$ revisited: quantitative analysis in terms of fluctuating superconducting pairs

“…We have checked that the T onset value determined from our resistivity measurements by using a background-independent procedure agrees, well within the corresponding experimental uncertainties, with those that may be inferred from the measurements of other research groups in the best available OPT Y-123 single-crystals and epitaxial films. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][28][29][30][31][32][33][34][35] Similarly, we have checked that the T onset we propose here from our magnetization measurements in the zero-field limit agrees with the results on the precursor diamagnetism onset that may be inferred from the χ(T ) H measurements of other authors in single-crystal and polycrystalline OPT Y-123 superconductors. [8][9][10][39][40][41] The conductivity and the magnetization around T c in OPT Y-123...…”

“…The confirmation of this prediction by measurements in different OPT HTSC (a result that will be extended in our present work to the high reduced temperature region, ε > 0.1) not only provided further support to the GGL scenario but also was an early indication of the absence of the so-called indirect fluctuation effects on both observables [25]. This conclusion concerns in particular the Maki-Thompson contribution to the in-plane paraconductivity [3][4][5]8,25], in agreement with the enhanced pair-breaking effects expected for the non-1 s 0 wave pairing in the HTSC [26,27]. The GL scenario was further supported by early scaling analyses of the electrical conductivity and the diamagnetism measured around T c (H) in the so-called critical region [28][29][30][31][32].…”

“…The ratio between ∆χ(ε) H and ∆σ ab (ε) has been earlier determined in Ref. [25] (only up to ε ≈ 0.1) and Ref. [40] (in this case up to ε ≈ 0.4).…”

“…The conductivity and the magnetization around T c in OPT Y-123... microbridge studied in the previous subsection are well within the dispersion expected for different high-quality OPT Y-123 samples. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][28][29][30][31][32][33][34][35][36][37][38][39][40][41] The magnetic susceptibility rounding above T c , that following the conventional denomination will already be called precursor diamagnetism, is orders of magnitude smaller than in the Meissner region. [3,8] Therefore, to measure these roundings one must apply magnetic fields orders of magnitude larger than those used in the ZFC measurements.…”

“…[25], this approach predicts that in the mean-field-like region where it is applicable, the fluctuations effects on both observables, the paraconductivity and the precursor diamagnetism, will have the same dependence on the reduced temperature, ε ≡ ln(T /T c ). The confirmation of this prediction by measurements in different OPT HTSC (a result that will be extended in our present work to the high reduced temperature region, ε > 0.1) not only provided further support to the GGL scenario but also was an early indication of the absence of the so-called indirect fluctuation effects on both observables [25]. This conclusion concerns in particular the Maki-Thompson contribution to the in-plane paraconductivity [3][4][5]8,25], in agreement with the enhanced pair-breaking effects expected for the non-1 s 0 wave pairing in the HTSC [26,27].…”