Diamagnetic activity above Tc as a precursor to superconductivity in La2-xSrxCuO4 thin films

Iguchi, Ienari; Yamaguchi, Takumi; Sugimoto, Akihiro

doi:10.1038/35086540

Cited by 136 publications

(106 citation statements)

References 25 publications

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“…We have already mentioned the recent measurements of magnetic domains above T c which has been interpreted as a diamagnetic precursor to the Meissner state, produced by performed pairs in underdoped La 2−x Sr x CuO 4 thin films 20 . The existence of superconducting clusters between T * and T c easily explains the appearance of local diamagnetic or Meissner domains and, if there is a temperature gradient in the sample, the local flux flows and produces the dynamic flux flow state 28 .…”

Section: Discussionmentioning

confidence: 99%

“…It reflects the nano-scale variations of the superconducting energy gap or the nano-scale variations on the density of charges in the material. This percolating scenario can be understood by analyzing the scanning SQUID microscopy magnetic data which makes a map of the expelled magnetic flux (Meissner effect) domains on LSCO films 20 . This experiment shows the regions where the Meissner effect continuously develops from near T * to temperatures well below the percolating threshold T c .…”

Section: Introductionmentioning

confidence: 99%

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Theory for high-Tcsuperconductors considering inhomogeneous charge distribution

2003

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We propose a general theory for the critical and pseudogap temperatures Tc and T * dependence on the doping concentration for high-Tc oxides, taking into account the charge inhomogeneities in the CuO2 planes. Several recent experiments have revealed that the charge density ρ in a given compound (mostly underdoped) is intrinsic inhomogeneous with large spatial variations which leads to a local charge density ρ(r). These differences in the local charge concentration yield insulator and metallic regions, either in an intrinsic granular or in a stripe morphology. In the metallic region, the inhomogeneous charge density produces also spatial or local distributions which form Cooper pairs at a local superconducting critical temperatures Tc(r) and zero temperature gap ∆0(r). For a given compound, the measured onset of vanishing gap temperature is identified as the pseudogap temperature, that is, T * , which is the maximum of all Tc(r). Below T * , due to the distribution of Tc(r)'s, there are some superconducting regions surrounded by insulator or metallic medium. The transition to a coherent superconducting state corresponds to the percolation threshold among the superconducting regions with different Tc(r)'s. The charge inhomogeneities have been studied by recent STM/S experiments which provided a model for our phenomenological distribution. To make definite calculations and compare with the experimental results, we derive phase diagrams for the BSCO, LSCO and YBCO families, with a mean field theory for superconductivity using an extended Hubbard Hamiltonian. We show also that this novel approach provides new insights on several experimental features of high-Tc oxides.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theory for high-Tcsuperconductors considering inhomogeneous charge distribution

2003

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“…This is another manifestation of the intrinsic tendency toward microscopically inhomogeneous states (the list of references simply too long to be reproduced here). Finally, recent scanning SQUID microscopy study by Iguchi et al [17] have reported the existence of diamagnetic activity above T c in La 2−x Sr x CuO 4 . The phenomenon is found at temperatures as high as 80 K, which is remarkable!…”

Section: Inhomogeneities In Manganites and Other Com-poundsmentioning

confidence: 99%

Nanoscale phase separation in colossal magnetoresistance materials: lessons for the cuprates?

Dagotto

Burgy

Moreo

2003

Solid State Communications

107

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A recent vast experimental and theoretical effort in manganites has shown that the colossal magnetoresistance effect can be understood based on the competition of charge-ordered and ferromagnetic phases. The general aspects of the theoretical description appear to be valid for any compound with intrinsic phase competition. In high temperature superconductors, recent experiments have shown the existence of intrinsic inhomogeneities in many materials, revealing a phenomenology quite similar to that of manganese oxides. Here, the results for manganites are briefly reviewed with emphasis on the general aspects. In addition, theoretical speculations are formulated in the context of Cu-oxides by mere analogy with manganites. This includes a tentative explanation of the spin-glass regime as a mixture of antiferromagnetic and superconducting islands, the rationalization of the pseudogap temperature T * as a Griffiths temperature where clusters start forming upon cooling, the prediction of "colossal" effects in cuprates, and the observation that quenched disorder may be far more relevant in Cu-oxides than previously anticipated.

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“…In particular, much of this discussion addresses the character of the local order in a quantum disordered phase close to a quantum critical 1 For brief reviews of the current evidence on various types of stripe order in the cuprates, see (Carlson et al, 2003;Castro Neto and Morais Smith, 2003;Emery et al, 1999;Orenstein and Millis, 2000;Sachdev, 2002;Zaanen, 2000) 2 Fluctuations associated with off-diagonal (i.e., superconducting) order are best studied using different strategies; see, for example, Iguchi et al, 2001;Jankó et al, 1999;Ussishkin et al, 2002;Wang et al, 2001;Xu et al, 2000) 3 For reviews of neutron and X-ray evidence of stripes, see (Emery et al, 1999;Tranquada, 1998a,b).…”

Section: Introductionmentioning

confidence: 99%

How to detect fluctuating stripes in the high-temperature superconductors

et al. 2003

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We discuss fluctuating order in a quantum disordered phase proximate to a quantum critical point, with particular emphasis on fluctuating stripe order. Optimal strategies for extracting information concerning such local order from experiments are derived with emphasis on neutron scattering and scanning tunneling microscopy. These ideas are tested by application to two model systemsthe exactly solvable one dimensional electron gas with an impurity, and a weakly-interacting 2D electron gas. We extensively review experiments on the cuprate high-temperature superconductors which can be analyzed using these strategies. We adduce evidence that stripe correlations are widespread in the cuprates. Finally, we compare and contrast the advantages of two limiting perspectives on the high-temperature superconductor: weak coupling, in which correlation effects are treated as a perturbation on an underlying metallic (although renormalized) Fermi liquid state, and strong coupling, in which the magnetism is associated with well defined localized spins, and stripes are viewed as a form of micro-phase separation. We present quantitative indicators that the latter view better accounts for the observed stripe phenomena in the cuprates.

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Diamagnetic activity above Tc as a precursor to superconductivity in La2-xSrxCuO4 thin films

Cited by 136 publications

References 25 publications

Theory for high-Tcsuperconductors considering inhomogeneous charge distribution

Theory for high-Tcsuperconductors considering inhomogeneous charge distribution

Nanoscale phase separation in colossal magnetoresistance materials: lessons for the cuprates?

How to detect fluctuating stripes in the high-temperature superconductors

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