Theory of high-temperature superconductivity: Application to YBCO systems

Kamimura, Hiroshi; Sano, Akihiro

doi:10.1007/bf02765703

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…In this case, 2n in equations ( 1) and ( 2) is 76. For insulating YBCO 6 , Sano et al [34,35] recently published the calculated result, and thus we omit describing their calculations in this article and simply present the result, together with those for YBCO 7 . In figure 4(a) the crystal structure of YBCO 7 is shown.…”

Section: Calculated Results For the Cuo 5 Pyramid In Ybco 7−δmentioning

confidence: 99%

“…The energy difference between the 3 B 1 and the 1 A 1 multiplets, as a function of the charge of a Cu(1) ion in a Cu-O chain, q, in a hole-doped CuO 5 cluster embedded in YBCO 6 and YBCO 7 . The closed circle represents the energy difference between the 3 B 1 and 1 A 1 multiplets in YBCO 6 [34,35]. The open circles represent the energy difference between the 3 B 1 and 1 A 1 multiplets in superconducting YBCO 7 as a function of constant q for all Cu(1) ions, where c is fixed at 2.29 Å.…”

Section: The Energy Difference Between the 1 A 1 And 3 B 1 Multiplets...mentioning

confidence: 99%

“…The calculated results are shown by solid diamonds in figure 5, where the energy differences between the 1 A 1 and 3 B 1 multiplets are shown on the vertical axis, and q on the horizontal axis represents the averaged charge of Cu(1) ions in a Cu-O chain. For comparison, we also show the energy difference between the 1 A 1 and 3 B 1 multiplets calculated for the case of a constant charge distribution in a Cu-O chain as a function of q [34,35].…”

Section: The Effect Of a Charge-density Wave (Cdw) In A Cu-o Chainmentioning

confidence: 99%

See 2 more Smart Citations

Theory of high-temperature superconductivity in underdoped cuprates; the unusual electronic structure and the origin of the pseudogap

Kamimura¹,

Nomura²,

Sano³

1998

J. Phys.: Condens. Matter

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By reviewing the first-principles studies of the many-electron electronic structures of underdoped and performed by Kamimura and co-workers, unusual electronic states are clarified. That is, the dopant holes move coherently by taking the Zhang-Rice spin singlet and Hund's coupling spin triplet alternately in the spin-correlated region of antiferromagnetic ordering due to the Cu localized spins, without destroying the antiferromagnetic order. This creates a metallic state which leads to superconductivity. The coexistence of (i) the antiferromagnetic spin ordering and (ii) the ordering in the appearance of the Zhang-Rice singlet and the Hund's coupling triplet results in the small Fermi surface for a carrier system and also leads to the decrease in the electronic entropy below a certain temperature at which the Fermi surface changes from a larger one to smaller ones. This is the microscopic origin of the pseudogap, the concept of which was originally proposed by Loram and co-workers in terms of the Fermi liquid picture.

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Section: Calculated Results For the Cuo 5 Pyramid In Ybco 7−δmentioning

confidence: 99%

Section: The Energy Difference Between the 1 A 1 And 3 B 1 Multiplets...mentioning

confidence: 99%

Section: The Effect Of a Charge-density Wave (Cdw) In A Cu-o Chainmentioning

confidence: 99%

See 1 more Smart Citation

Theory of high-temperature superconductivity in underdoped cuprates; the unusual electronic structure and the origin of the pseudogap

Kamimura¹,

Nomura²,

Sano³

1998

J. Phys.: Condens. Matter

Self Cite

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“…We showed [21,3,4] that the ε for Γ is close to one, while the ε for D ee is large. This follows from the local nature of ε [33,25,4].…”

Section: ) the Large Value Of ∆γ/γ Bardeenmentioning

confidence: 99%

“…We believe that the large ε may be related to a new degeneracy between the Zhang-Rice singlet and the anti Jahn-Teller triplet of the CuO 5 complex. Kamimura et al [25] calculated the splitting between the singlet and triplet as function of the occupation of the 3d shell of the chain copper, and found that for 0.55 holes there, these states are degenerate. This calculation is carried out using a quantum-chemistry algorithm.…”

Section: ) Vertex Correction Including the Ionic Dielectric Functionmentioning

confidence: 99%

Vertex corrections in nearly ferroelectric superconductors

Fay

Weger

2000

Phys. Rev. B

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We investigate the effect of an incipient ferrolectric transition on vertex corrections to the superconducting pairing interaction. The vertex corrections for small momentum transfers are large independent of the type of Boson responsible for the superconducting transition. The electron-phonon interaction is found to be enhanced by a nearly ferroelectric medium. We discuss application to the cuprate superconductors.Comment: 7 pages, 4 figures, published in Phys. Rev. B 62, 15208 (2000

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Estimation of the influence of ionic dielectricity on the dynamic superconducting order parameter

1998

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Abstract. We consider the influence of an w-dependent ionic dielectric constant ~( w ) on the properties of a superconductor. Assuming that the pairing interaction is proportional to c2 we have solved the Eliashberg equations for this case, both for imaginary and real frequencies. The interaction potential depends on a coupling constant J. and on a longitudinal phonon frequency Q. The dielectric constant is assumed to be independent of wavevector q, and to depend on frequency through the expression: ~( w )where wlong, wvans are the frequencies of optical phonons of the dielectric. We find that along the imaginary frequency axis (but not for real frequencies) the weighted phonon propagator can be modeled by an appropriate choice of a cutoff frequency and an effective coupling constant. The influence of ~( w )on I " ' , the gap d(w), and the renormalization function Z(w) are studied and it is found that these quantities increase significantly with the dielectric constant.

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Theory of high-temperature superconductivity: Application to YBCO systems

Cited by 9 publications

References 14 publications

Theory of high-temperature superconductivity in underdoped cuprates; the unusual electronic structure and the origin of the pseudogap

Theory of high-temperature superconductivity in underdoped cuprates; the unusual electronic structure and the origin of the pseudogap

Vertex corrections in nearly ferroelectric superconductors

Estimation of the influence of ionic dielectricity on the dynamic superconducting order parameter

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