Interplay of Electron‐Lattice Interactions and Superconductivity in Bi2Sr2CaCu2O8+δ

Lee, Jinho; Fujita, Kazuhiro; McElroy, K.; Slezak, J.; Wang, M.; Aiura, Y.; Bando, Hiroshi; Ishikado, M.; Masui, T.; Zhu, Juntao

doi:10.1002/chin.200645010

Cited by 21 publications

(54 citation statements)

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“…The strength and form of the peak reflects those of the DOS singularity. This feature agrees with experiments of Lee et al [1]. A weaker signal also appears displaced by twice the phonon energies in agreement with experiment.…”

supporting

confidence: 93%

“…One point of divergence between the theory and the spectra reported by Lee et al is the presence of a sharp minimum in the calculated d 2 I/dV 2 spectra just above the peak. The STM experiments of Lee et al [1] show substantial spatial variations in the spectra with a clear correlation between the frequency shift of the side peaks and the local value of the superconducting energy gap. Such a correlation follows if the local bosonic mode couples directly to the planar holes and if this electron-boson coupling is involved in the superconductivity.…”

mentioning

confidence: 89%

“…For the superconductor we assume for simplicity a d-wave type DOS N s (ε) ∝ n s (ε) = Re ε/ √ ε 2 − ∆ 2 cos 2 θ θ . However, in the experiment [1] the shape of the superconducting DOS varies strongly from point to point. Since the phonon involves mainly the motion of the apical oxygen atoms we assume an optical phonon band centered around frequency Ω 0 with a weak dispersion (i.e.…”

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confidence: 94%

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Role of Inelastic Tunneling through the Insulating Barrier in Scanning-Tunneling-Microscope Experiments on Cuprate Superconductors

Pilgram

Rice²,

Sigrist³

2006

Phys. Rev. Lett.

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The tunneling path between the CuO2-layers in cuprate superconductors and a scanning tunneling microscope tip passes through a barrier made from other oxide layers. This opens up the possibility that inelastic processes in the barrier contribute to the tunneling spectra. Such processes cause one or possibly more peaks in the second derivative current-voltage spectra displaced by phonon energies from the density of states singularity associated with superconductivity. Calculations of inelastic processes generated by apical O-phonons show good qualitative agreement with recent experiments reported by Lee et al. [1]. Further tests to discriminate between these inelastic processes and coupling to planar phonons are proposed.PACS numbers: 74.25.Kc,74.50.+r,68.37.Ef The importance of the electron-phonon interaction in the high temperature cuprate superconductors has long been a matter of debate. In conventional superconductors tunneling experiments analyzed by McMillan and Rowell [2] not only unequivocally established that the exchange of phonons between electrons is the underlying mechanism for Cooper pairing but also allowed its spectroscopic determination. In the case of cuprates there are many good reasons to doubt the dominance of an attraction due to phonon exchange. These reasons range from the d-wave rather than s-wave pairing symmetry, to their electronic structure as lightly doped Mott insulators. The latter points toward a strong onsite Coulomb repulsion which cannot be treated perturbatively, violating a key postulate in the standard BCS-Eliashberg theory. A number of proposals have been made for a subdominant role for the electron-phonon interactions particularly involving the half-buckling phonon modes which couple attractively in the d-wave pairing channel [3,4,5,6,7,8].Very recently, a new set of tunneling measurements at low temperatures has been reported by Lee et al. [1] using a STM (Scanning Tunneling Microscope). Results with this local tunneling probe show considerable variations in the form and energy of the density of states (DOS) singularity associated with the superconductivity and also a peak in the second derivative current-voltage spectra which is displaced from the DOS peak by a fairly constant energy. Lee et al. [1] report further that isotope substitution on the O-ions shifts this energy consistent with a phonon origin for this peak. This raises the question whether these spectra should be interpreted analogously to those of conventional superconductors or if these peaks have another source.A series of works explain the appearence of side peaks in the DOS of d-wave superconductors in terms of localized bosonic modes [9], resonant spin modes [10,11] or the breathing mode phonons [12]. All these proposals consider inelastic processes that happen directly in the superconducting plane. In this letter we examine an alternative explanation in terms of inelastic tunneling processes. Such inelastic processes are well established in electron tunneling spectroscopy [13,14,15,16] of metal-insu...

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supporting

confidence: 93%

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confidence: 89%

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confidence: 94%

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Role of Inelastic Tunneling through the Insulating Barrier in Scanning-Tunneling-Microscope Experiments on Cuprate Superconductors

Pilgram

Rice²,

Sigrist³

2006

Phys. Rev. Lett.

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“…The peaks in G͑V͒ vary from V = 0.7⌬ / e to ⌬ / e. However, even though P͑k y ͒ varies drastically with k y when there is little scattering by the O 2− ions, the corresponding G͑V͒ curves are more rounded than those observed experimentally, especially recently. 5,22 Within the present approach even higher k-space selectivity may be needed to account for the experimental STS data. There are several ways in which this might occur.…”

Section: Discussionmentioning

confidence: 98%

Scanning tunneling spectroscopy gap maps of cuprate single crystals:k-space anisotropy as an alternative to nanoscale inhomogeneity

Cooper

2007

Phys. Rev. B

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The results of a computer analysis of a simple two-dimensional quantum mechanical tunneling model are reported. These suggest that the spatial dependence of the superconducting energy gap observed by scanning tunneling spectroscopy ͑STS͒ studies of single crystals of the high T c superconductor Bi 2 Sr 2 CaCu 2 O 8+x is not necessarily caused by nanoscale inhomogeneity. Instead, the spatial dependence of the STS data could arise from the momentum ͑k͒ dependence of the energy gap, which is a defining feature of a d-wave superconductor. In other words, the superconducting properties of the CuO 2 layers could be spatially uniform. It is possible that this viewpoint could be exploited to obtain k-dependent information from STS studies.

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“…There is growing consensus that it originates from some form of density-wave like competing order (which could include coupling to phonons) [36][37][38] , and may actually also involve several competing modes, again due to proximity to the …”

Section: Optical Spectra In Electron Andmentioning

confidence: 99%

Optical model-solution to the competition between a pseudogap phase and a charge-transfer-gap phase in high-temperature cuprate superconductors

2010

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We present a theoretical framework for a quantitative understanding of the full doping dependence of the optical spectra of the cuprates. In accord with experimental observations, the computed spectra show how the high-energy Mott features continue to persist in the overdoped regime even after the mid-infrared (MIR) peak originating from the pseudogap has collapsed in a quantum critical point. In this way, we reconcile the opposing tendencies of the MIR and Mott peaks to shift in opposite directions in the optical spectra with increasing doping. The competition between the pseudogap and the Mott gap also results in rapid loss of spectral weight in the high energy region with doping.

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Interplay of Electron‐Lattice Interactions and Superconductivity in Bi₂Sr₂CaCu₂O_8+δ

Cited by 21 publications

References 1 publication

Role of Inelastic Tunneling through the Insulating Barrier in Scanning-Tunneling-Microscope Experiments on Cuprate Superconductors

Role of Inelastic Tunneling through the Insulating Barrier in Scanning-Tunneling-Microscope Experiments on Cuprate Superconductors

Scanning tunneling spectroscopy gap maps of cuprate single crystals:k-space anisotropy as an alternative to nanoscale inhomogeneity

Optical model-solution to the competition between a pseudogap phase and a charge-transfer-gap phase in high-temperature cuprate superconductors

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