Electromagnetic response of superconductors and optical sum rule

Karakozov, A. E.; Maksimov, E. G.; Dolgov, O. V.

doi:10.1016/s0038-1098(02)00486-6

Cited by 25 publications

(58 citation statements)

References 24 publications

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“…This means that the observed increase in the superconducting state represents a lower bound on the increase. This result is in the opposite direction of the estimate of Karakozov et al 17 ; their result was made for the dirty limit (Mattis-Bardeen 19 ) result, which turns out to have high frequency properties that are very distinct from those with non-infinite scattering rate. The conclusion is that the increase in the optical spectral weight in the superconducting state does indeed suggest a decrease in kinetic energy, or, in more conventional language, a collapse of electronic scattering, in the superconducting state 13,20,21 .…”

Section: Kubocontrasting

confidence: 58%

Impact of a finite cut-off for the optical sum rule in the superconducting state

2008

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A single band optical sum rule derived by Kubo can reveal a novel kind of superconducting state. It relies, however, on a knowledge of the single band contribution from zero to infinite frequency. A number of experiments over the past five years have used this sum rule; their data has been interpreted in support of 'kinetic energy-driven superconductivity'. However, because of the presence of unwanted interband optical spectral weight, they necessarily have to truncate their sum at a finite frequency. This work examines theoretical models where the impact of this truncation can be examined first in the normal state, and then in the superconducting state. The latter case is particularly important as previous considerations attributed the observed anomalous temperature dependence as an artifact of a non-infinite cutoff frequency. We find that this is in fact not the case, and that the sign of the corrections from the use of a non-infinite cutoff is such that the observed temperature dependence is even more anomalous when proper account is taken of the cutoff. On the other hand, in these same models, we find that the strong observed temperature dependence in the normal state can be attributed to the effect of a non-infinite cutoff frequency.

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Section: Kubocontrasting

confidence: 58%

Impact of a finite cut-off for the optical sum rule in the superconducting state

2008

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“…By using the EPI spectral function α 2 (ω)F(ω) from tunnelling measurements and by assuming α 2 6. We stress that the recent elipsometric measurements of the dielectric function ε(ω) [75] confirms this theoretical prediction [82].…”

Section: Dynamical Conductivity σ (ω)supporting

confidence: 55%

“…The latter must incorporate relevant scattering mechanisms and bands. Such calculations were done in [82] by taking into account the large EPI interaction. By using the EPI spectral function α 2 (ω)F(ω) from tunnelling measurements and by assuming α 2 6.…”

Section: Dynamical Conductivity σ (ω)mentioning

confidence: 99%

“…Calculated theoretical T-dependence of high-energy part of the sum ruleĀ H (ω c = 1.25eV, 2ω c = 2.5eV ) by taking into account the electron-phonon interaction. The data from [82] in the semiconductor range and We discuss briefly the in-plane resistivity ρ a−b (T ) only, because its temperature behavior is a direct consequence of the quasi-2D motion of quasiparticles and of the inelastic scattering which they suffer. At present there is no consensus on the origin of the linear temperature dependence of the inplane resistivity ρ a−b (T ) in the normal state.…”

Section: Resistivity ρ(T )mentioning

confidence: 99%

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Electron-Phonon Interaction and Strong Correlations in High-Temperature Superconductors: One can not avoid the unavoidable

Kulić¹

2004

AIP Conference Proceedings

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Abstract. The important role of the electron-phonon interaction (EPI) in explaining the properties of the normal state and pairing mechanism in high-T c superconductors (HTSC) is discussed. A number of experimental results are analyzed such as: dynamical conductivity, Raman scattering, neutron scattering, ARPES, tunnelling measurements, isotope effect and etc. They give convincing evidence that the EPI is strong and dominantly contributes to pairing in HTSC oxides. It is argued that strong electronic correlations in conjunction with the pronounced (in relatively weakly screened materials) EPI are unavoidable ingredients for the microscopic theory of pairing in HTSC oxides. I present the well defined and controllable theory of strong correlations and the EPI. It is shown that strong correlations give rise to the pronounced forward scattering peak in the EPI -the FSP theory. The FSP theory explains in a consistent way several (crucial) puzzles such as much smaller transport coupling constant than the pairing one (λ tr ≪ λ ), which are present if one interprets the results in HTSC oxides by the old Migdal-Eliashberg theory for the EPI. The ARPES shift puzzle where the nodal kink at 70 meV is unshifted in the superconducting state, while the anti-nodal one at 40 meV is shifted can be explained at present only by the FSP theory. A number of other interesting predictions of the FSP theory are also discussed.

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“…19 In Ref. 5, the effect of the cutoff was considered in the context of electrons coupled to phonons. The goal of the present paper is to study the influence of the cutoff on the optical integral for a model of electrons interacting with a broad spectrum of bosons that two of us have used previously to model optics data.…”

mentioning

confidence: 99%

Optical integral in the cuprates and the question of sum-rule violation

Norman

Chubukov²,

Heumen

et al. 2007

Phys. Rev. B

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Much attention has been given to a possible violation of the optical sum rule in the cuprates and the connection this might have to kinetic energy lowering. The optical integral is composed of a cutoffindependent term ͑whose temperature dependence is a measure of the sum-rule violation͒, plus a cutoffdependent term that accounts for the extension of the Drude peak beyond the upper bound of the integral. We find that the temperature dependence of the optical integral in the normal state of the cuprates can be accounted for solely by the latter term, implying that the dominant contribution to the observed sum-rule violation in the normal state is due to the finite cutoff. This cutoff-dependent term is well modeled by a theory of electrons interacting with a broad spectrum of bosons.

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Electromagnetic response of superconductors and optical sum rule

Cited by 25 publications

References 24 publications

Impact of a finite cut-off for the optical sum rule in the superconducting state

Impact of a finite cut-off for the optical sum rule in the superconducting state

Electron-Phonon Interaction and Strong Correlations in High-Temperature Superconductors: One can not avoid the unavoidable

Optical integral in the cuprates and the question of sum-rule violation

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