Structure and physical properties of single crystals of the 84-K superconductor<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Bi</mml:mi></mml:mrow><mml:mrow><mml:mn>2.2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Sr</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ca</mml:mi></

Sunshine, Steven A.; Siegrist, T.; Schneemeyer, Lynn; Murphy, D. W.; Cava, R. J.; Batlogg, B.; Dover, R. B. van; Fleming, R. M.; Glarum, S. H.; Nakahara, S.; Farrow, R. C.; Krajewski, J. J.; Zahurak, S. M.; Waszczak, J. V.; Marshall, J. H.; Marsh, P.; Rupp, L. W.; Peck, W. F.

doi:10.1103/physrevb.38.893

Cited by 660 publications

(62 citation statements)

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“…According to experiments [30][31][32][33] , the BSCCO-2212 crystal has a pseudo-tetragonal substructure unit cell, as seen in Figure 2( impurities in adjacent super cell, which allow us to study the effect of the impurity on the first through third nearest neighbor Cu atoms. In the z direction, we use only half of the primitive unit cell ( ) 2 c , because the interaction with the other half is so weak that the omission of it does not affect the surface properties in our test calculations.…”

Section: Computational Detailsmentioning

confidence: 99%

Ab initiocalculation of impurity effects in copper oxide materials

2005

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We describe a method for calculating, within density functional theory, the electronic structure associated with typical defects which substitute for Cu in the CuO 2 planes of high-T c superconducting materials. The focus is primarily on Bi 2 Sr 2 CaCu 2 O 8 , the material on which most STM measurements of impurity resonances in the superconducting state have been performed. The magnitudes of the effective potentials found for Zn, Ni and vacancies on the in-plane Cu sites in this host material are remarkably consistent with phenomenological fits of potential scattering models to STM resonance energies. The effective potential ranges are quite short, of order 1 Å with weak long range tails, in contrast to some current models of extended potentials which attempt to fit STM data.For the case of Zn and Cu vacancies, the effective potentials are strongly repulsive, and states on the impurity site near the Fermi level are simply removed. The local density of states (LDOS) just above the impurity is nevertheless found to be a maximum in the case of Zn and a local minimum in case of the vacancy, in agreement with experiment. The Zn and Cu vacancy patterns are explained as due to the long-range tails of the effective impurity potential at the sample surface. The case of Ni is richer due to the Ni atom's strong hybridization with states near the Fermi level; in particular, the short range part of the potential is attractive, and the LDOS is found to vary rapidly with distance from the surface and from the impurity site. We propose that the current controversy surrounding the observed STM patterns can be resolved by properly accounting for the effective impurity potentials and wave-functions near the cuprate surface. Other aspects of the impurity states for all three species are discussed.2

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Section: Computational Detailsmentioning

confidence: 99%

Ab initiocalculation of impurity effects in copper oxide materials

2005

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“…[22] Finally, small differences in cation stoichiometry, and hence disorder, affects the change of oxygen stoichiometry for the same annealing conditions. [16] The P b−doped BSCCO has attracted much attention since Sunshine et al [23] found that the substitution of lead can enhance the superconducting temperature T c in BSCCO multiphase. It was then found that the lead substitution has a strong influence on the incommensurate modulation that exists in the b−axis.…”

Section: Introductionmentioning

confidence: 99%

Pb0.4Bi1.6
Ma
¹
,
Alméras
²
,
Kelley
³

et al. 1995
Phys. Rev. B

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“…The crystal structure of Bi2212 is more realistically modeled as a √ 2 × √ 2 orthorhombic unit cell 16 . Accordingly, Fig.…”

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Raising Bi-O Bands above the Fermi Energy Level of Hole-DopedBi2Sr2CaCu2O8+δand Other Cuprate Superconductors

et al. 2006

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The Fermi surface (FS) of Bi2Sr2CaCu2O 8+δ (Bi2212) predicted by band theory displays Birelated pockets around the (π, 0) point, which have never been observed experimentally. We show that when the effects of hole doping either by substituting Pb for Bi or by adding excess O in Bi2212 are included, the Bi-O bands are lifted above the Fermi energy (EF ) and the resulting first-principles FS is in remarkable accord with measurements. With decreasing hole-doping the Bi-O bands drop below EF and the system self-dopes below a critical hole concentration. Computations on other Bias well as Tl-and Hg-based compounds indicate that lifting of the cation-derived band with hole doping is a general property of the electronic structures of the cuprates.PACS numbers: 74.72. Hs,74.25.Jb,71.18.+y, First-principles band theory computations on the cuprates have become a widely accepted tool for gaining insight into their electronic structures, spectral properties, Fermi surfaces (FS's), and as a starting point for constructing theoretical models for incorporating strong correlation effects beyond the framework of the local-density approximation (LDA) underlying such calculations 1,2,3,4 . For example, in the double layer Bicompound Bi 2 Sr 2 CaCu 2 O 8+δ (Bi2212) − perhaps the most widely investigated cuprate − the LDA generated band structure 5,6 is commonly invoked to describe the doped metallic state of the system. Band theory however clearly predicts the FS of Bi2212 to contain a FS pocket around the antinodal point M (π, 0) as a Bi-O band drops below the Fermi energy (E F ), but such FS pockets have never been observed experimentally 7 . This 'Bi-O pocket problem' is quite pervasive and occurs in other Bi-compounds. 8 Similarly, Tl-and Hg-compounds display cation-derived FS pockets, presenting a fundamental challenge for addressing on a first-principles basis issues related to the doping dependencies of the electronic structures of the cuprates.In this Letter, we show how the cation-derived band responsible for the aforemenentioned FS pockets is lifted above E F when hole doping effects are properly included in the computations. Detailed results for the case of Bi2212 are presented, where hole doping is generated either by substituting Pb for Bi or by adding excess oxygen in the Bi-O planes. With 20% Pb doping in the orthorhombic crystal structure, the Bi-O band lies ≈ 1 eV above E F and the remaining bonding and antibonding FS sheets are in remarkable accord with the angleresolved photoemission (ARPES) measurements on an overdoped Bi2212 single crystal 9 . Below a critical hole doping level, the Bi-O band falls below E F and, as a result of this self-doping effect, further reduction in the hole doping level no longer reduces the number of holes in the CuO 2 layers. We argue that the underlying mechanism at play here is that hole doping reduces the effective positive charge in the Bi-O donor layers, which then reduces the tendency of the electrons to 'flow back' and self-dope the material. We have also carried out computatio...

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Structure and physical properties of single crystals of the 84-K superconductorBi2.2Sr2Ca

Cited by 660 publications

References 3 publications

Ab initiocalculation of impurity effects in copper oxide materials

Ab initiocalculation of impurity effects in copper oxide materials

Pb0.4Bi1.6
Ma
¹
,
Alméras
²
,
Kelley
³

et al. 1995
Phys. Rev. B

Raising Bi-O Bands above the Fermi Energy Level of Hole-DopedBi2Sr2CaCu2O8+δand Other Cuprate Superconductors

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Structure and physical properties of single crystals of the 84-K superconductorBi2.2Sr2Ca

Cited by 660 publications

References 3 publications

Ab initiocalculation of impurity effects in copper oxide materials

Ab initiocalculation of impurity effects in copper oxide materials

Pb0.4Bi1.6Ma1, Alméras2, Kelley3 et al. 1995Phys. Rev. B

Raising Bi-O Bands above the Fermi Energy Level of Hole-DopedBi2Sr2CaCu2O8+δand Other Cuprate Superconductors

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Pb0.4Bi1.6
Ma
¹
,
Alméras
²
,
Kelley
³

et al. 1995
Phys. Rev. B