On the distribution of intrinsic holes in cuprates

Stoll, E.; Meier, P. F.; Claxton, T. A.

doi:10.1088/0953-8984/15/46/007

Cited by 6 publications

(6 citation statements)

References 25 publications

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“…It ist further concluded that materials with higher T C,max have larger hopping ranges and in materials with highest T C,max the axial orbital, essentially a hybrid between Cu4s, Cu3d 3z 2 −1 and apical oxygen 2p z , is almost pure Cu4s. Moreover, the importance of Cu4s for an accurate description of the partial charge distributions in the HTSC's is pointed out applying the "local ansatz" ab initio method, which allows to add correlations as corrections to a Hartree-Fock ground state 25 or density functional theory 29 , respectively. Now we address the question concerning the possible nature of a superconducting state of the HTSC's that would be consistent with our modeling of the normal state.…”

Section: B Qualitative Discussion Of the Modeling Of The Electronic S...mentioning

confidence: 99%

Modeling the electronic state of the high-TcsuperconductorLaCuO: Phonon dynamics and charge response

2006

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A modeling of the normal state of the p-doped high-temperature superconductors (HTSC's) is presented. This is achieved starting from a more conventional metallic phase for optimal-and overdoping and passing via the underdoped to the insulating state by consecutive orbital selective compressibility-incompressibility transitions in terms of sum rules for the charge response. The modeling is substantiated by corresponding phonon calculations. Extending investigations of the full dispersion and in particular of the strongly doping dependent anomalous phonon modes in LaCuO, which so far underpin our treatment of the density response of the electrons in the pdoped HTSC's, gives additional support for the modeling of the electronic state, compares well with recent experimental data and predicts the dispersion for the overdoped regime. Moreover, phonon densities of states have been calculated and compared for the insulating, underdoped, optimally doped and overdoped state of LaCuO. From our modeling of the normal state a consistent picture of the superconducting phase also can be extracted qualitatively pointing in the underdoped regime to a phase ordering transition. On the other hand, the modeling of the optimal and overdoped state is consistent with a quasi-particle picture with a well defined Fermi surface. Thus, in the latter case a Fermi surface instability with an evolution of pairs of well defined quasiparticles is possible and can lead to a BCS-type ordering. So, it is tempting to speculate that optimal TC in the HTSC's marks a crossover region between these two forms of ordering.

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Section: B Qualitative Discussion Of the Modeling Of The Electronic S...mentioning

confidence: 99%

Modeling the electronic state of the high-TcsuperconductorLaCuO: Phonon dynamics and charge response

2006

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“…The holes thus introduced on the oxygens destroy rapidly the long range antiferromagnetic order and the materials become conducting. Although we have pointed out elsewhere 20,21 that this picture is too naive and may easily lead to wrong conclusions, a semiquantitative discussion on the values of the oxygen charges and their changes with hole and electron doping both in the unsubstituted and in the Zn substituted compound is instructive. We have therefore indicated in Fig.…”

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confidence: 97%

Charge and spin density distributions around Zn impurities in cuprates

Bersier¹,

Renold²,

Stoll³

et al. 2005

Phys. Rev. B

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The effect of zinc substitution on the local electronic structure of several cuprates is investigated using first-principles cluster calculations. Clusters comprising 5, 9, and 13 copper atoms in the cuprate plane of La2CuO4, YBa2Cu3O7, and YBa2Cu4O8 are used. Spin polarized calculations with different multiplicities in the framework of density functional theory enable a detailed study of the changes in the charge and spin density distribution induced by Zn substitution. Furthermore, doping with charge carriers in the above materials is simulated and the resulting changes in the charge distribution are compared to the changes induced by Zn impurities. These differences are then discussed in terms of a phenomenological model related to properties expected from the generic phase diagram. The effects of zinc substitution are rather local and as expected the absolute values of the Mulliken charges at both nearest and next nearest neighbor oxygens to Zn are larger than in the unsubstituted clusters. The calculated electric field gradient at Cu sites that are nearest neighbor to Zn is found to be somewhat larger than in the unsubstituted cluster whereas that of next nearest neighbors is about 5 % smaller. We conclude that the satellite peak in the Cu NQR spectrum occurring upon Zn substitution in YBa2Cu3O7 and YBa2Cu4O8 has its origin at Cu that are next nearest neighbors to Zn.

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“…We obtain ρ 0 (3) = −0.012 that is close to zero which emphasizes the suitability of these clusters to represent the local conditions of atoms in the crystal. This point cannot be overstressed since it also means that there is now also confidence in the partial Mulliken populations of the individual orbitals which have been studied in detail elsewhere [22].…”

Section: Modelmentioning

confidence: 99%

“…The copper and the planar oxygen atoms, however, are rather covalently bound and the relation between charge and hole transfer is not trivial. A Mulliken charge population analysis [22] attributes a charge of 1.16 to the copper and −1.64 to the planar oxygens but 40% of the hole is transferred to the oxygens leaving 60% on the copper. Since a hole transfer is accompanied by an electron charge transfer in the opposite direction it is concluded that of the total of 0.84 electrons transferred from the oxygen to the copper, 0.40 electrons are accounted for the hole transfer.…”

Section: Modelmentioning

confidence: 99%

Ab initio calculations of the electronic structure of cuprates using large scale cluster techniques

Renold,

Bersier,

Stoll

et al. 2007

Preprint

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The local electronic structures of La2CuO4, three members of the Yttrium-family (YBa2Cu3O6, YBa2Cu3O7, and YBa2Cu4O8), and to some extent of Nd2CuO4 have been determined using allelectron ab-initio cluster calculations for clusters comprising up to thirteen planar copper atoms associated with their nearest planar and apical oxygen atoms. Spin-polarized calculations in the framework of density functional theory have enabled an estimation of the superexchange couplings J. Electric field gradients at the planar copper sites are determined and their dependence on the occupation of the various atomic orbitals are investigated in detail. The changes of the electronic field gradient and of the occupation of orbitals upon doping are studied and discussed. Furthermore, magnetic hyperfine fields are evaluated and disentangled into on-site and transferred contributions, and the chemical shifts at the copper nucleus are calculated. In general the results are in good agreement with values deduced from experiments except for the value of the chemical shift with applied field perpendicular to the CuO2-plane.

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On the distribution of intrinsic holes in cuprates

Cited by 6 publications

References 25 publications

Modeling the electronic state of the high-TcsuperconductorLaCuO: Phonon dynamics and charge response

Modeling the electronic state of the high-TcsuperconductorLaCuO: Phonon dynamics and charge response

Charge and spin density distributions around Zn impurities in cuprates

Ab initio calculations of the electronic structure of cuprates using large scale cluster techniques

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