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Roa-Rojas, J.; Costa, Rosângela Menegotto; Pureur, P.; Prieto, P.

doi:10.1103/physrevb.61.12457

Cited by 71 publications

(42 citation statements)

References 29 publications

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“…4, below T c , in the approach to the zero resistance state, we observe a characteristic scaling in χ −1 σ (T ) curves, for experimental data, in absence of magnetic field and for several values of transport current density. This result has the characteristic feature of the high temperature superconductors for low applied magnetic fields [1,8]. For the analysis of this fluctuation regime, we assume that ∆σ is given by equation (2), but using the critical exponent s and the reduced temperature ε =…”

Section: Resultsmentioning

confidence: 99%

“…2(a) and 2(b) permit to separate two good differenced regimes: first, for high temperature, we observe one sharp maximum in dρ (T ) dT , which is related with intra-granular fluctuations (fluctuations in the amplitude of the order parameter). These characteristic fluctuations define the so called pairing transition [8]. The temperature value of this maximum is close to the bulk critical temperature value T c .…”

Section: Analysis Methodsmentioning

confidence: 99%

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Pairing and coherence transition in La1.82Sr0.18CuO4 strongly two-dimensional superconductor

Roa-Rojas¹,

Téllez²,

Sarmiento³

2006

Braz. J. Phys.

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We report conductivity fluctuation measurements in the La 1.82 Sr 0.18 CuO 4 high temperature superconducting material. The conductivity fluctuation analysis was performed by utilizing the concept of the logarithmic derivative of the conductivity excess. Close and above the critical temperature T c , we experimentally determine the occurrence of Gaussian and critical fluctuation regimes. Systematic measurements of conductivity as a function of temperature were performed for several values of transport current j. Fluctuation analysis close to the zero resistivity temperature T c0 was performed and we clearly identified a characteristic exponent, which is analyzed by the dynamical scaling theory and considering a percolation-like transition in a frustrated and disordered system. The observation of a glass-like behavior in our experiments permits to interpret our results as corresponding to a vortex-glass regime.

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Section: Resultsmentioning

confidence: 99%

Section: Analysis Methodsmentioning

confidence: 99%

Pairing and coherence transition in La1.82Sr0.18CuO4 strongly two-dimensional superconductor

Roa-Rojas¹,

Téllez²,

Sarmiento³

2006

Braz. J. Phys.

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“…For s ≈ 3.0 exponent, Rosenblatt proposed an interpretation based on a paracoherent-coherent transition of the artificially prepared granular arrays [28,29]. The powerlaw regime with exponent approximately s = 3 was also observed in granular samples of YBa 2 (Cu 3−x Zn x )O 7−δ [30], GdBa 2 Cu 3 O 7−δ [31] and Bi 1.6 Pb 0.4 Sr 2 Ca n−1 Cu n O x (n = 2 or n = 3) [21] near the zero resistance state.…”

Section: Fluctuation Regimesmentioning

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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“…Careful studies of the conductivity in the neighborhood of the critical temperature can yield information about the nature of the superconducting state [14][15][16] as well as on the influence of the granularity at microscopic and mesoscopic levels on the fluctuation regimes [17][18][19]. In this paper, we report on fluctuations conductivity measurements in polycrystalline samples of the Er 1−x Pr x Ba 2 Cu 3 O 7−δ (0 ≤ x ≤ 0.10) superconductor.…”

Section: Introductionmentioning

confidence: 99%

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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Pairing transition, coherence transition, and the irreversibility line in granularGdBa2Cu3O

Cited by 71 publications

References 29 publications

Pairing and coherence transition in La1.82Sr0.18CuO4 strongly two-dimensional superconductor

Pairing and coherence transition in La1.82Sr0.18CuO4 strongly two-dimensional superconductor

Conductivity fluctuations of polycrystalline Ag-doped YBa2Cu3O7-δ superconductor

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

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