Critical chain length and superconductivity emergence in oxygen-equalized pairs ofYBa2Cu3O<

Abstract

The oxygen-order dependent emergence of superconductivity in YBa 2 Cu 3 O 6+x is studied, for the first time in a comparative way, on pair samples having the same oxygen content and thermal history, but different Cu(1)O x chain arrangements deriving from their intercalated and deintercalated nature. Structural and electronic non-equivalence of pairs samples is detected in the critical region and found to be related, on microscopic scale, to a different average chain length, which, on being experimentally determined by nuclear quadrupole resonance (NQR), sheds new light on the concept of critical chain length for hole doping efficiency.74.25.Dw; 61.14. x; 76.60.Gv;Typeset using REVT E X 1

A link between critical transition temperature and the structure of superconducting

“…It has been found [1][2][3][4] that T c does not vary monotonically with concentration. Beside the maximum transition temperature at O 6.96 [5] there is a plateau or second local maximum [3] at O 6.55 with a temperature of T c = 57 K [1][2][3][4]. This variation of the transition temperature as a function of oxygen deficiency has been confirmed qualitatively by experimental data by many papers.…”

Magnetic states of lightly hole-doped cuprates in the clean limit as seen via zero-field muon spin spectroscopy

“…The absence of spurious phases is confirmed by systematic x-ray Rietveld refinements, and the oxygen content has been fixed by a topotactic technique, which consists in the oxygen equilibration of stoichiometric quantities of two end members (y = 0.05(2) and y = 0.98(1)), packed in sealed vessels with minimum free volume. 76,77 Low temperature annealing produces homogeneous samples, with well ordered CuO chains in the basal plane, with an absolute error of δy = ±0.01 in oxygen content per formula unit (cross checked by iodometric titration and thermogravimetry on each sample). The mobile carrier content is obtained from systematic measurements of the room temperature Seebeck coefficient, 78 with a calibration procedure 41 of the exponential dependence of S vs h, performed on empty-chain Y 1−x Ca y Ba 2 Cu 3 O 6 samples.…”

Singling out the effect of quenched disorder in the phase diagram of cuprates

“…The Cu(1)-i site i = 2, 3, 4, distinguished by their nearestneighbor, are shown in the bottom inset (see text); the top inset shows Cu(1)-2.j sites, j = 0, 1, 2 with three distinct next-nearest-neighbor environments, justifying the fine splitting of the Cu(1)-2 peaks. assignment 12,18,27 , the narrow doublet peak at 24 MHz and 22 MHz is due to the Cu(1)-3 configuration. The large peaks at ≈ 22 MHz is due to Cu(1)-4 sites from longer chain fragments.…”

“…By comparison with clean limit YBa 2 Cu 3 O 6+y this provides the pure effect of quenched disorder in a crucial region of the phase diagram. (2), was achieved following a topotactic-like low temperature annealing 18,19 of stoichiometric quantities of fully oxidized and fully reduced specimens (y = 0.98(2) and y = 0.05(2), respectively), tightly packed in vessels sealed in vacuum. The low temperature annealing allows the diffusion of the mobile species O(1) inside the material towards the minimum energy configuration.…”