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Uemura, Masuji

doi:10.6089/jscm.7.74

Cited by 15 publications

(18 citation statements)

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“…In fact, they are not far from the BCS to BE crossover, defined as shown by Pistolesi and Strinati by the condition (k F ξ pair ) = 1. One of the manifestations of this proximity is the Uemura plot T c ∝ λ −2 followed by all underdoped cuprates (Uemura, 2002). Another one is the observation of strong fluctuation effects in the heat capacity transition.…”

Section: Some Comments On the Pseudogapmentioning

confidence: 99%

Andreev–Saint-James reflections: A probe of cuprate superconductors

2005

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Electrical transport through a normal metal / superconductor contact at biases smaller than the energy gap can occur via the reflection of an electron as a hole of opposite wave vector. The same mechanism of electron-hole reflection gives rise to low energy states at the surface of unconventional superconductors having nodes in their order parameter. The occurrence of electron-hole reflections at normal metal / superconductor interfaces was predicted independently by Saint James and de Gennes and by Andreev, and their spectroscopic features discussed in detail by Saint James in the early sixties. They are generally called Andreev reflections but, for that reason, we call them Andreev -Saint James (ASJ) reflections. We present a historical review of ASJ reflections and spectroscopy in conventional superconductors, and review their application to the High Tc cuprates. The occurrence of ASJ reflections in all studied cuprates is well documented for a broad range of doping levels, implying that there is no large asymmetry between electrons and holes near the Fermi level in the superconducting state. In the underdoped regime, where the pseudo-gap phenomenon has been observed by other methods such as NMR, ARPES and Giaever tunneling, gap values obtained from ASJ spectroscopy are smaller than pseudo-gap values, indicating a lack of coherence in the pseudo-gap energy range. Low energy surface bound states have been observed in all studied hole doped cuprates, in agreement with a dominant d-wave symmetry order parameter. Results are mixed for electron doped cuprates. In overdoped Y Ba 2 Cu 3 O 7−δ (δ < 0.08) and La 2−x SrxCuO 4 , ASJ spectroscopy is consistent with the presence of an additional imaginary component of the order parameter. Results of ASJ spectroscopy under applied magnetic fields are also reviewed. A short section at the end is devoted to some recent results on spin effects. * Electronic address: guyde@tau.ac.il 2

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Section: Some Comments On the Pseudogapmentioning

confidence: 99%

Andreev–Saint-James reflections: A probe of cuprate superconductors

2005

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“…Another interesting point concerning this material is that some experiments suggest possible occurrence of an unconventional superconductivity, [2 -5] although there are also experiments suggesting conventional pairing [6]. In particular, an unchanged Knight shift across T c found in some experiments suggests spin-triplet pairing [3], while absence of broken time reversal symmetry [7,8] may exclude possibility of chiral p-wave or d-wave pairing states, leaving spin-triplet f-wave pairing as a good candidate.…”

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confidence: 99%

“…Since the nodes of the f-wave gap intersects the large Fermi surface, this can account for the experimental results suggesting the existence of gap nodes. In fact, it has recently been found that a muon spin relaxation data can be well explained by taking this view [8]. Another point to be mentioned in relation with the experiments is that the pocket Fermi surfaces are not observed in angle-resolved photoemission spectroscopy (ARPES) experiments [29,30] up to date.…”

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confidence: 99%

Possible Spin-Tripletf-Wave Pairing Due to Disconnected Fermi Surfaces In NaxCoO2·yH2O

2004

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We propose that the spin-triplet pairing mechanism due to disconnected Fermi surfaces proposed in our previous study [Phys. Rev. B 63, 174507 (2001)]] may be at work in a recently discovered superconductor NaxCoO2.yH2O. We introduce a single band effective model that takes into account the pocketlike Fermi surfaces along with the van Hove singularity near the K point found in the band calculation results. Applying the fluctuation exchange method and solving the linearized Eliashberg equation, the most dominant pairing is found to have spin-triplet f-wave symmetry, where the nodes of the gap function do not intersect the pocket Fermi surfaces. The presence of finite Tc is suggested in sharp contrast to cases when the gap nodes intersect the Fermi surface.

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“…The magnetic field penetration depth λ of superconductors is related to the superconducting carrier density n s divided by the effective mass m * as 1/λ 2 ∝ n s /m * . In a recent paper Uemura [27] explained the experimental data found in [28] assuming a microscopic phase separation between superfluid and non-superconducting fermionic carriers, similar to the superfluid He films. Recently, it was reported that, the photoemission spectra near the Brillouin zone boundary, exhibit unexpected sensitivity to the superfluid density [29], supporting the universality as function of doping and temperature of the properties of the cuprates.…”

Section: Resultsmentioning

confidence: 99%

“…We calculated the London penetration depth and the c-axis and ab-plane conductivity and compared the results with the experimental data. The study of experimental dependence of the penetration depth is an important problem [27,28].…”

Section: Discussionmentioning

confidence: 99%

Transport properties calculation in the superconducting state for a quasi-two-dimensional system

Moca

Macocian

2001

Physica C: Superconductivity

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We performed a self-consistent calculation of the transport properties of a d-wave superconductor. We used for calculations the T-matrix approximation. The coresponding equations were evaluated numerically directly on the real frequecy axis. We studied the ab-plane charge dynamics in the coherent limit. For the c-axis charge dynamics, we considered both, the coherent and the incoherent limit. We also have calculated the penetration depth in this model.

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Cited by 15 publications

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Andreev–Saint-James reflections: A probe of cuprate superconductors

Andreev–Saint-James reflections: A probe of cuprate superconductors

Possible Spin-Tripletf-Wave Pairing Due to Disconnected Fermi Surfaces In NaxCoO2·yH2O

Transport properties calculation in the superconducting state for a quasi-two-dimensional system

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