Splitting of the bulk resistive transition in high-Tc superconductors: Evidence for unconventional pairing

Costa, Rosângela Menegotto; Jurelo, Alcione Roberto; Rodrigues, Pedro; Pureur, P.; Schaf, J.; Kunzler, J. V.; Ghivelder, L.; Campá, J.A.; Rasines, I.

doi:10.1016/0921-4534(95)00399-1

Cited by 20 publications

(19 citation statements)

References 28 publications

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“…Feeble features of split superconducting transitions are often present in experimental data. 8,[20][21][22] However, in our Y 1−x Pr x Ba 2 Cu 3 O 7−␦ samples they are so explicit and clear-cut that it is impossible to ignore them. Even seeming somewhat exotic they constitute an important morphological possibility that should be known by the experts in superconducting materials.…”

Section: Discussionmentioning

confidence: 89%

“…Their contribution can be estimated by subtracting from the extrapolated linear resistivity, defined by the data well above T c , the effectively measured resistivity. Assuming that the excess electric conductivity ⌬͑T͒ diverges when the temperature approaches T c from above according to the power law 21,25 …”

Section: B Fluctuation Magnetoconductivitymentioning

confidence: 99%

“…Nevertheless, the observation of quite analogous split transitions in the single crys-tals with no trace of structural inhomogeneity strongly indicated a more unusual inhomogeneity. Split resistive transitions have often been observed in HTSC samples, 7,8,10,[19][20][21][22] but in general could be attributed to conventional sample inhomogeneities. This, however, is not possible anymore in the case of our single crystals.…”

Section: Introductionmentioning

confidence: 99%

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Unconventional superconducting granularity of theY1−xPrxBa2Cu3
Barros
¹
,
Pureur
²
,
Schaf
³

et al. 2006
Phys. Rev. B
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We report on fluctuation magnetoconductivity and magnetic irreversibility of Y 1−x Pr x Ba 2 Cu 3 O 7−␦ single crystals and a polycrystalline sample. Although our samples are all single phase ͑orthorhombic͒ and the single crystals show no sign of structural inhomogeneity, all the samples exhibit two close and sharp genuine superconducting transitions. On the other hand, while the resistive transition of the polycrystalline sample exhibits in addition a coherence transition characteristic of a granular superconductor and the magnetic irreversibility displays the signature of the intergrain flux dynamics, the single crystals show no sign of these features. In view of these facts, we conclude that the well characterized split superconducting transition must result from a peculiar phase separation related with oxygen doping.

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Section: Discussionmentioning

confidence: 89%

Section: B Fluctuation Magnetoconductivitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Unconventional superconducting granularity of theY1−xPrxBa2Cu3
Barros
¹
,
Pureur
²
,
Schaf
³

et al. 2006
Phys. Rev. B
Self Cite
33
5
31
0
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“…However, this two‐peak splitting was observed in many other studied samples, such as in doped samples Y 1– x Pr x Ba 2 Cu 3 O 7– δ (single crystals and polycrystalline) 7, 8 and Er 1– x Pr x Ba 2 Cu 3 O 7– δ (polycrystalline) 32. Also, it was observed in a polycrystalline Bi (2– x ) Pb x Sr 2 Ca 2 Cu 3 O 10 (Bi‐2223) sample 8 and in single crystals of Bi 2 Sr 2 CaCu 2 O 8 (Bi‐2212) 33.…”

Section: Resultsmentioning

confidence: 95%

Fluctuation‐induced conductivity of (YCe)Ba₂Cu₃O_7–δ superconductor

Ferreira

Pinheiro

Júnior

et al. 2011

Physica Status Solidi (b)

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Phone: þ55 42 220 3044, Fax: þ55 42 220 3042Systematic measurements of the in-plane and out-of-plane in conductivity fluctuations have been used to investigate the role of the cerium ion on the splitting of the pairing transition. This splitting, associated with a phase separation, was firstly observed in single crystals and polycrystalline samples of Y 1-x Pr x Ba 2 Cu 3 O 7-d . Considering that Ce is the rare-earth element most easily ionized to the þ4 state and that in melttextured sample, it is possible to observe anisotropic effects, we examined the effect of this ion in the Y 1-x Ce x Ba 2 Cu 3 O 7-d compound. We prepared three different samples: polycrystalline, pure melt-textured and Ce-doped melt-textured. Melttextured samples were prepared using the top-seeding growth technique and the polycrystalline sample by the standard solid-state reaction technique. The samples were characterized by X-ray diffraction, scanning electron microscopy (SEM) and electrical resistivity. To identify power-law divergences in the conductivity, the results were analyzed in terms of the temperature derivative of the resistivity (dr=dT) and of the logarithmic temperature derivative of the conductivity (ÀdlnðDsÞ=dT). In the normal phase, Gaussian and critical regimes were clearly seen for melt-textured samples and no important differences between pure and Cedoped samples were observed. On the other hand, for the polycrystalline sample and from the critical exponent analysis, a splitting of the pairing transition was clearly observed. It is suggested that the occurrence of a phase separation and its association with Ce doping as already observed for Pr-doped samples. form an important family of superconducting materials with critical temperatures around 92 K. RE signifies the rare-earth elements except for Ce, Pr, and Tb. These elements have in common the possibility of existing in a tetravalent state [1,2], and Ce, Pr, and Tb, in that order, are the three rare-earth elements most easily ionized to the þ4 state. Several explanations have been proposed for the absence of superconductivity and the depression of critical temperature T C in (Pr-Ce)Ba 2 Cu 3 O 7-d . Some studies suggest that a tetravalent ionic state would lead to compensation or back filling of holes in the CuO 2 planes introduced by oxygenation [3]. The effect of Ce substitution in the RE-123 has been discussed in the framework of the existing models for the Pr system, and besides the hole-filling model [3], some other models such as hole localization [4], magnetic pair breaking [5], and percolation [6] have been proposed to explain the degradation of superconductivity.

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“…21 This phase separation may elucidate the occurrence of the two close genuine superconducting transitions often observed in cuprates. 6,22,23 Although considerable progress has been made in the polycrystalline Y 1−x Ca x Ba 2 Cu 3 O 7−␦ materials, only very few attempts have succeeded in growing Y 1−x Ca x Ba 2 Cu 3 O 7−␦ single crystals. [24][25][26] Moreover, sample analysis showed that the single crystals, grown by the self-flux method, contain a Ca concentration much lower than the nominal concentration.…”

Section: Introductionmentioning

confidence: 99%

Granular superconductivity in a Ca-dopedYBa2Cu3O7−δsingle crystal: Role of divalent

2007

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We investigate the effect of the divalent Ca atoms at the trivalent Y site of YBa 2 Cu 3 O 7−␦ on the magnetoconductivity and magnetic irreversibility of single crystals and a polycrystalline sample. The magnetic irreversibility displays the de Almeida-Thouless and Gabay-Toulouse power laws, the signature of a frustrated superconducting grain aggregate for the H ʈ c axis as well as for the H ʈ ab plane. The resistive transition for measuring current along the ab plane and H ʈ c axis is a clear two step process. While the upper temperature step is only weakly affected by applied fields, the lower temperature transition is visibly broadened and shifted down to lower temperatures. We impute the upper temperature step to the pairing transition within grains while the lower temperature step is due to grain coupling and coherence transition. For the J ʈ ab and H ʈ ab planes, the resistive transition is a one step process and the effect of the applied fields is very weak for H ʈ J as well as for H Ќ J. We explain these observations in terms of the directional anisotropy of the phase displacements between the superconducting grains and their weakening effect on the grain coupling, caused by the applied field. We also compare our present results with those of YBa 2 Cu 3 O 7−␦ single crystals doped with the trivalent Pr at the Y site and with divalent elements such as Zn or Mg at the Cu site and Sr at the Ba site and suggest that the valence as well as the local breaking of the orbital symmetry by impurities plays an important role in the induction of superconducting granularity.

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Splitting of the bulk resistive transition in high-Tc superconductors: Evidence for unconventional pairing

Cited by 20 publications

References 28 publications

Unconventional superconducting granularity of theY1−xPrxBa2Cu3
Barros
¹
,
Pureur
²
,
Schaf
³

et al. 2006
Phys. Rev. B
Self Cite
33
5
31
0
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Unconventional superconducting granularity of theY1−xPrxBa2Cu3
Barros
¹
,
Pureur
²
,
Schaf
³

et al. 2006
Phys. Rev. B
Self Cite
33
5
31
0
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Fluctuation‐induced conductivity of (YCe)Ba₂Cu₃O_7–δ superconductor

Granular superconductivity in a Ca-dopedYBa2Cu3O7−δsingle crystal: Role of divalent

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Splitting of the bulk resistive transition in high-Tc superconductors: Evidence for unconventional pairing

Cited by 20 publications

References 28 publications

Unconventional superconducting granularity of theY1−xPrxBa2Cu3Barros1, Pureur2, Schaf3 et al. 2006Phys. Rev. BSelf Cite335310View full textAdd to dashboardCite

Unconventional superconducting granularity of theY1−xPrxBa2Cu3Barros1, Pureur2, Schaf3 et al. 2006Phys. Rev. BSelf Cite335310View full textAdd to dashboardCite

Fluctuation‐induced conductivity of (YCe)Ba2Cu3O7–δ superconductor

Granular superconductivity in a Ca-dopedYBa2Cu3O7−δsingle crystal: Role of divalent

Contact Info

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Resources

About

Unconventional superconducting granularity of theY1−xPrxBa2Cu3
Barros
¹
,
Pureur
²
,
Schaf
³

et al. 2006
Phys. Rev. B
Self Cite
33
5
31
0
View full text Add to dashboard Cite

Unconventional superconducting granularity of theY1−xPrxBa2Cu3
Barros
¹
,
Pureur
²
,
Schaf
³

et al. 2006
Phys. Rev. B
Self Cite
33
5
31
0
View full text Add to dashboard Cite

Fluctuation‐induced conductivity of (YCe)Ba₂Cu₃O_7–δ superconductor