Observation of the Finite Superconducting Gap States in La1.86Sr0.14CuO4-xby Electron Tunneling

Murakami, Hironaru; Ohbuchi, Syuzo; Aoki, Ryôzô

doi:10.1143/jpsj.63.2653

Cited by 15 publications

(6 citation statements)

References 9 publications

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“…If we now assume that spin fluctuations are the primary pairing excitation, then we would replace the substrate that was a very good phonon propagator with a substrate that would not support the propagation of high-energy phonons but was magnetic and would be an excellent BaKBiO systems could be selected for the initial study. In accordance with Murakami et al (1994), the LaSrCuO compound also has a sharp gap and could represent a good candidate for this experiment as well. As for YBCO and other cuprates, they are usually characterized by a gapless spectrum.…”

Section: Proposed Experimentssupporting

confidence: 55%

Colloquium: Electron–Lattice Interaction and Its Impact on High-T_c Superconductivity

Kresin

Wolf

2020

Peking University-World Scientific Advanced Physics Series

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In this Colloquium , the main features of the electron-lattice interaction are discussed and high values of the critical temperature up to room temperature could be provided. While the issue of the mechanism of superconductivity in the high T c cuprates continues to be controversial, one can state that there have been many experimental results demonstrating that the lattice makes a strong impact on the pairing of electrons. The polaronic nature of the carriers is also a manifestation of strong electronlattice interaction. One can propose an experiment that allows an unambiguous determination of the intermediate boson (phonon, magnon, exciton, etc.) which provides the pairing. The electron-lattice interaction increases for nanosystems, and this is due to an effective increase in the density of states.insulators. Doping leads to conductivity and then, for larger carrier concentration, to superconductivity. There is some characteristic value of the carrier concentration, n m , which corresponds to the maximum value of T c ≡ T c max . The underdoped (nn m ) regions are characterized by values of T c lower than T c max .Since the discovery of high T c oxides , there has been an intensive and fruitful study of these novel materials . However, despite intensive research, the question of the mechanism for these materials is still open.There has been growing evidence, mainly from various experimental studies, that the electron-lattice interaction is important for understanding the nature of high T c superconductivity in the cuprates. This interaction provides a direct contribution to the pairing of electrons, and also is clearly manifested in polaronic effects. The polaronic effects appear as a result of the strong electron-lattice interaction. In this case, a moving electron polarizes the lattice, and a shift in positions of neighboring ions forms a potential "box" for the electron. A polaron is a unit containing an electron that is moving with the lattice polarization caused by the electron itself (see,e.g., Ashcroft and Mermin,1976; Devresee, 2005, and see Sec.IV).This Colloquium is not a review, but rather a systematic description of our view, reflected in many publications on the subject. This Colloquium 9 also contains an extensive list of references that are related to this subject.Our viewpoint is that the electron-lattice interaction is an important ingredient of the current scenario and can explain superconductivity in novel systems including high temperature superconducting cuprates.The structure of the paper is as follows.The general properties of superconductivity caused by the electron-phonon interaction are discussed in Sec..II. Experimental data demonstrating the impact of this interaction are described in Sec.III. Section IV is concerned with the polaronic effect and the isotopic substitution. The phonon-plasmon mechanism for layered systems is described in Sec.V. Section VI contains a discussion of the electron-lattice interaction in the "pseudogap" state. A critical experiment...

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Section: Proposed Experimentssupporting

confidence: 55%

Colloquium: Electron–Lattice Interaction and Its Impact on High-T_c Superconductivity

Kresin

Wolf

2020

Peking University-World Scientific Advanced Physics Series

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“…Asymmetric SC peaks corresponding to ∆/T c ≤ 4 have been reported for LSCO in Ref. 71 , Tl-2201 in Ref. 66 Tl-2212 in Ref.…”

Section: Contradicting Evidencementioning

confidence: 67%

Hypothesis of two-dimensional stripe arrangement and its implications for the superconductivity in high-Tccuprates

Fine

2004

Phys. Rev. B

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The hypothesis that holes doped into high-Tc cuprate superconductors organize themselves in two-dimensional (2D) array of diagonal stripes is discussed, and, on the basis of this hypothesis, a new microscopic model of superconductivity is proposed and solved. The model describes two kinds of hole states localized either inside the stripes or in the antiferromagnetic domains between the stripes. The characteristic energy difference between these two kinds of states is identified with the pseudogap. The onset of superconductivity is caused by the interaction, which is assumed to be mediated by the transverse fluctuations of stripes. The superconducting (SC) order parameter predicted by the model has two components, whose quantum phases exhibit a complex dependence on the the center-of-mass coordinate. The model predictions for the tunneling characteristics and for the dependence of the critical temperature (Tc) on the superfluid density show good quantitative agreement with a number of experiments. The model, in particular, predicts that the SC peaks in the tunneling spectra are asymmetric, only when ∆/Tc > 4, where ∆ is the SC gap. It is also proposed that, at least in some high-Tc cuprates, there exist two different superconducting states corresponding to the same doping concentration and the same critical temperature. Finally, the checkerboard pattern in the local density of states observed by scanning tunneling microscopy in Bi2Sr2CaCu2O 8+δ is interpreted as coming from the states localized around the centers of stripe elements forming the 2D superstructure.

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“…The break-junction tunneling data on BSCCO, YBCO, its 60 K phase ͑YBCO-60 K͒ and La 2Ϫx Sr x CuO 4Ϫx ͑LSCO͒ are indicated by solid squares. [82][83][84] The pointcontact junction data from Nd 2Ϫx Ce x CuO 4Ϫy NCCO, the noncuprate Ba 1Ϫx K x BiO 3 ͑BKBO͒ and Hg-1201 are indicated by solid triangles. 85,41 The ARPES data for BSCCO are indicated by asterisks.…”

Section: Data Interpretation and Discussionmentioning

confidence: 99%

Quasiparticle tunneling spectra of the high-Tcmercury cuprates: Implications of thed-wave two-dimensional van Hove scenario

Wei

Tsuei²,

Bentum

et al. 1998

Phys. Rev. B

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Quasiparticle tunneling measurements of the high-temperature superconductors HgBa 2 Ca nϪ1 Cu n O 2nϩ2ϩ␦ (Hg-12(nϪ1)n,nϭ1,2,3) are considered in the context of d x 2 Ϫy 2 symmetry of the superconducting order parameter and a two-dimensional ͑2D͒ van Hove singularity ͑vHs͒ related to saddle points in the electronic band structure. Normal-metal-insulator-superconductor tunneling spectra taken at 4.2 K with a scanning tunneling microscope on Hg-1212 c-axis epitaxial films, as well as on Hg-1201 and Hg-1223 polycrystalline samples, show distinct gap characteristics which cannot be easily reconciled with the simple s-wave BCS density of states. The data are analyzed with the nodal d-wave gap function ⌬ k ϭ⌬ 0 (cos k x Ϫcos k y )/2 and the 2D tight-binding electronic dispersion k ϭϪ2t(cos k x ϩcos k y )ϩ4tЈ(cos k x cos k y )Ϫ, using the quasiparticle tunneling formalism for elastic and specular transmission. The analysis indicates a highly directional and energy-dependent spectral weighting, related to the gap anisotropy and band-structure dependence of the tunneling matrix element ͉T͉ 2 , and successfully explains the observed gap spectra. Values for the d-wave gap maximum are determined to be ⌬ 0 Ϸ33, 50, and 75 meV, respectively, for optimally doped Hg-1201, Hg-1212, and Hg-1223, corresponding to reduced-gap ratios of 2⌬ 0 /k B T c Ϸ7.9, 9.5, and 13. These ratios are substantially larger than the BCS weak-coupling limit of 3.54. A comparison with data from other high-T c cuprates indicates an overall trend of 2⌬ 0 /k B T c rising with T c , in violation of BCS universality.

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Observation of the Finite Superconducting Gap States in La_1.86Sr_0.14CuO_4-xby Electron Tunneling

Cited by 15 publications

References 9 publications

Colloquium: Electron–Lattice Interaction and Its Impact on High-T_c Superconductivity

Colloquium: Electron–Lattice Interaction and Its Impact on High-T_c Superconductivity

Hypothesis of two-dimensional stripe arrangement and its implications for the superconductivity in high-Tccuprates

Quasiparticle tunneling spectra of the high-Tcmercury cuprates: Implications of thed-wave two-dimensional van Hove scenario

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Observation of the Finite Superconducting Gap States in La1.86Sr0.14CuO4-xby Electron Tunneling

Cited by 15 publications

References 9 publications

Colloquium: Electron–Lattice Interaction and Its Impact on High-Tc Superconductivity

Colloquium: Electron–Lattice Interaction and Its Impact on High-Tc Superconductivity

Hypothesis of two-dimensional stripe arrangement and its implications for the superconductivity in high-Tccuprates

Quasiparticle tunneling spectra of the high-Tcmercury cuprates: Implications of thed-wave two-dimensional van Hove scenario

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Product

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Observation of the Finite Superconducting Gap States in La_1.86Sr_0.14CuO_4-xby Electron Tunneling

Colloquium: Electron–Lattice Interaction and Its Impact on High-T_c Superconductivity

Colloquium: Electron–Lattice Interaction and Its Impact on High-T_c Superconductivity