Effect of reduction in the density of states on fluctuation conductivity in Bi2Sr2CaCu2O8+x single crystals

Chowdhury, P.; Bhatia, S.N.

doi:10.1016/s0921-4534(99)00302-0

Cited by 6 publications

(14 citation statements)

References 21 publications

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“…In the Pr-free samples, the resistivity remains linear right down to ϳ120 K. The onset of the gap ͑if any͒ there appears to be masked by the thermal fluctuations which appear at around the same temperature. 25 It may be pointed out that a linearly varying (T) at high temperatures can also result from the scattering of electrons by phonons, but such a process gives a concave (T) vs T curve ͑Bloch-Gruniesen relation͒ whereas the shapes of the curves in the present case are distinctly convex. 14 10 have suggested that the anomalous normal-state properties of high-T c cuprates can be explained by using a variation in the uniform resonating-valence-bond ͑RVB͒ model in which fermions and spinless bosons are coupled by a gauge field.…”

Section: Results and Analysismentioning

confidence: 57%

Localization of charge carriers by Pr in theTl2Ba2Ca1

et al. 2002

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We have measured the resistivity and thermoelectric power of Tl 2 Ba 2 Ca 1Ϫx Pr x Cu 2 O y samples with xр0.6 in the temperature range 10-300 K. T c decreases with an increase in the Pr concentration and a crossover from a metallic to insulator state is observed in samples with xӍ0.4. In the highly resistive samples (xϾ0.4) conduction is governed by the in-plane variable range hopping of the carriers while in others, localization of bosons appears to be dominating. A ''spin gap'' is observed in the resistivity of these samples. The resistivity and thermoelectric power show the localization of the carriers to increase with an increase in Pr concentration. These data, examined in the light of existing models of conduction by localized carriers, show a preference for the model proposed by Nagaosa and Lee wherein the fermion contribution decreases and that of the bosons increases with the increase in the Pr concentration. The Pr L 3 -edge absorption data show Pr to be present in the mixed (3 ϩ and 4 ϩ ) valent state. Correlating the hole density ''p'' determined from T c and thermoelectric power with the valence of Pr estimated from x-ray-absorption edge measurements, we find hole filling along with hybridization to be the dominant mechanism for destablization and eventual suppression of superconductivity in these materials.

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Section: Results and Analysismentioning

confidence: 57%

Localization of charge carriers by Pr in theTl2Ba2Ca1

et al. 2002

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“…About the MT terms, their contribution was reliably investigated only recently, after that the importance of the DOS term was completely understood. 8 These experiments, performed both in a magnetic field 9,10,11,12,13 and in zero field, 12,14 share the conclusion that the MT process is unimportant. The purpose of the present work is to show that an accurate analysis of the zero-field paraconductivity measured in ideal experimental conditions can lead to very different conclusions, setting the anomalous MT term as the most important throughout the whole temperature range of validity of the superconducting fluctuation model.…”

Section: Introductionmentioning

confidence: 81%

Possible dominance of the Maki–Thompson process in the fluctuation conductivity of Bi-2212 superconducting whiskers

Truccato¹,

Agostino²,

Rinaudo³

et al. 2006

J. Phys.: Condens. Matter

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We report the measurement of the a-axis fluctuation conductivity in zero field for Bi2Sr2CaCu2O8+x microcrystals. A good geometrical characterization and an original method for data analysis allow to determine its temperature behaviour to a high accuracy. The correct application of the complete fluctuation theory [A. A. Varlamov et al., Adv. Phys. 48, 655 (1999)], with a minor correction for thek factor, leads to the conclusion that the anomalous MT term is the most important contribution throughout the whole temperature range of interest. More traditional alternative interpretations of the experimental data are also investigated and their inconsistency is demonstrated. This implies an s-wave symmetry for the order parameter and could provide a physical mechanism for the preformed pair scenario.

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“…On the other hand, Livanov et al [7] found significant amounts of σ DOS to be present in their studies on thin films of BSCCO. We had earlier shown [8] that the peak in the c-axis resistivity of BSCCO resulted due to the fluctuations of the order parameter and the DOS conductivity was present in significant amount in the entire mean field region. We have now measured the in-plane resistivity of single crystals of BSCCO and Tl 2 Ba 2 CaCu 2 O 8+δ (TBCCO) and find their fluctuation conductivities also contain the DOS contribution and conform better to the model proposed by Dorin et al [5].…”

Section: Introductionmentioning

confidence: 99%

Fluctuation conductivity in cuprate superconductors

Bhatia

2002

Pramana - J Phys

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We have measured the in-plane resistivity of Bi 2 Sr 2 CaCu 2 O 8+δ and Tl 2 Ba 2 CaCu 2 O 8+δ single crystals in the temperature range 70-300 K. The thermodynamic fluctuations in the conductivity of both the samples start around ∼ 125 K. We find the Lawrence and Doniach [1] model to be inadequate to describe the fluctuation conductivity in these materials. The modification suggested by Ramallo et al [4] where by the conductivity is enhanced due to the presence of two superconducting layers in each unit cell is also not adequate. We suggest the fluctuation conductivity to be reduced due to the reduction in the density of states (DOS) of the quasiparticles which results due to the formation of Cooper pairs at the onset of the fluctuations. The data agrees with the theory proposed by Dorin et al [5] which takes into account this reduction in DOS.

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Effect of reduction in the density of states on fluctuation conductivity in Bi2Sr2CaCu2O8+x single crystals

Cited by 6 publications

References 21 publications

Localization of charge carriers by Pr in theTl2Ba2Ca1

Localization of charge carriers by Pr in theTl2Ba2Ca1

Possible dominance of the Maki–Thompson process in the fluctuation conductivity of Bi-2212 superconducting whiskers

Fluctuation conductivity in cuprate superconductors

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