Coherence transition in granular high temperature superconductors

Jurelo, Alcione Roberto; Castillo, I Abrego; Roa-Rojas, J.; Mendonça-Ferreira, L.; Ghivelder, L.; Pureur, P.; Rodrigues, Pedro

doi:10.1016/s0921-4534(98)00617-0

Cited by 79 publications

(53 citation statements)

References 25 publications

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“…This regime is interpreted as being intrinsically related to superconducting granularity at mesoscopic level. When the disorder at mesoscopic level dominates, the fluctuation conductivity near the zero-resistance state must diverge with an exponent quite large (s ∼ = 3.0) [31]. The value s ∼ 2.9 observed for this sample is according to the expected value for critical conductivity fluctuations in artificially prepared granular arrays, s ∼ = 3 [32].…”

Section: Critical Fluctuation Regimessupporting

confidence: 53%

“…The disappearance of this regime is cleary related with the increase in Pr doping. The observation of the Gaussian regime is related with its robustness against the Pr doping.Again, in approaching the zero resistance state, our results show a power-law behavior with critical exponent s = 2.7 ± 0.1 that corresponds to a phase transition from a paracoherent to a coherent state of the granular array [31]. These results indicate that an increasing Pr concentration destroys the pairing critical regimes.…”

Section: Critical Fluctuation Regimesmentioning

confidence: 57%

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Analysis of fluctuation conductivity of polycrystalline Er1-xPr xBa2Cu3O7-δsuperconductors

et al. 2009

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In this work we report on conductivity fluctuation measurements in polycrystalline samples of the Er 1−x Pr x Ba 2 Cu3O 7−δ superconductor (x =0.00, 0.05 and 0.10). Samples were prepared by a standard solidstate reaction technique. The results were analyzed in terms of the temperature derivative of the resistivity and of the logarithmic temperature derivative of the conductivity that allowed the identification of power-law divergences of the conductivity. The results show that the transition proceeds in two stages: pairing and coherence transition. Also, our results, from the critical exponent analysis, show a two-peak splitting at pairing transition, indicating possibly a phase separation. On approaching the zero resistance state, our results show a power-law behavior that corresponds to a phase transition from paracoherent to a coherent state of the granular array.

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Section: Critical Fluctuation Regimessupporting

confidence: 53%

Section: Critical Fluctuation Regimesmentioning

confidence: 57%

Analysis of fluctuation conductivity of polycrystalline Er1-xPr xBa2Cu3O7-δsuperconductors

et al. 2009

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“…Decreasing the temperature, but above T C2 , we observe that χ −1 σ shows again another power law regime given by λ cr ∼ = 0.33±0.02. Below T C2 and near the zero resistance state the fluctuation conductivity is described by another power law with exponent s ∼ = 2.0, and it is interpreted as being intrinsically related to superconducting granularity from mesoscopic level [15]. other power law with exponent s 1 ∼ = 3.0.…”

Section: B Fluctuation Regimesmentioning

confidence: 97%

Fluctuation conductivity of polycrystalline Y1-xPr xBa2Cu3O7-delta superconductors

Jurelo¹,

Araújo²,

Siqueira³

et al. 2005

Braz. J. Phys.

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We studied the effect of superconducting fluctuations on the electrical conductivity of granular samples of Y 1−x Pr x Ba 2 Cu 3 O 7−δ superconductors, with x =0.01, 0.03, 0.05, 0.07 and 0.10. Samples were prepared by the standard solid-state reaction technique, with two different types of calcination process, in air at 900˚C ( x ≤ 0.07 ) and in vacuum at 850˚C ( 0.05 ≤ x ≤ 0.10 ). For the samples prepared in air, our results revealed a splitting of the bulk transition, denoted by T C1 and T C2 , besides the coherence transition. It was observed fluctuation regimes above the highest transition ( T C1 ) and the lowest transition ( T C2 ). For the samples calcinated in vacuum and high concentrations of Pr, changes were observed in the critical region with chemical substitution of the Pr ion for the Y ion. In the regime of approach to the zero resistance state it was observed an occurrence of a coherence transition for all concentrations of praseodymium.

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“…3(a) we show a plot of the derivative dρ/dT versus temperature for all samples. The maximum of dρ/dT , denoted by T P , corresponds approximately to the bulk critical temperature [17]. (111) Ag (200) Ag ( 92.3 K for GD, showing that the GB sample has the highest T P .…”

Section: Characterizationmentioning

confidence: 99%

“…From conductivity measurements and fluctuationinduced conductivity analysis, it is possible to separate what is granularity at microscopic and mesoscopic levels [19]. A small peak or an asymmetry in dρ/dT , at the temperature region below T P , occurs systematically in polycrystalline samples, indicating that the transition is a two-step process [17]. As the temperature decreases, it is first observed a pairing transition and then a coherence transition.…”

Section: Characterizationmentioning

confidence: 99%

Conductivity fluctuations of polycrystalline Ag-doped YBa2Cu3O7-δ superconductor

et al. 2010

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Systematic conductivity measurements near T C in granular Ag-doped YBa 2 Cu 3 O 7−δ superconductors are presented. Silver doped YBa 2 Cu 3 O 7−δ samples were produced by different routes and characterized by X-ray diffraction, dc magnetization and electrical resistivity. The results were analyzed in terms of the temperature derivative of the resistivity and of the logarithmic temperature derivative of the conductivity, that allowed identifying power-law divergences in the conductivity. The results show that the resistive transition proceeds in two stages. In the normal phase, Gaussian and critical fluctuation conductivity regimes were identified. Close to the zero-resistance temperature, a coherence transition related to the connective nature of the granular samples was evidenced. It was not observed significant differences in critical and Gaussian fluctuations between pure and Ag-doped YBa 2 Cu 3 O 7−δ polycrystalline samples.

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Coherence transition in granular high temperature superconductors

Cited by 79 publications

References 25 publications

Analysis of fluctuation conductivity of polycrystalline Er1-xPr xBa2Cu3O7-δsuperconductors

Analysis of fluctuation conductivity of polycrystalline Er1-xPr xBa2Cu3O7-δsuperconductors

Fluctuation conductivity of polycrystalline Y1-xPr xBa2Cu3O7-delta superconductors

Conductivity fluctuations of polycrystalline Ag-doped YBa2Cu3O7-δ superconductor

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