Origin of electric-field gradients in high-temperature superconductors

YBa2Cu3O7

Jaejun Yu, Arthur J Freeman, R. Podloucky, P. Herzig, P. Weinberger

Research output: Contribution to journalArticle

59 Citations (Scopus)

Abstract

The origin of the electric-field gradients (EFG) at nuclear sites in the high-Tc superconductor YBa2Cu3O7 is investigated theoretically by means of highly precise local-density full-potential linearized-augmented-plane-wave calculations. In all cases considered (i.e., at Cu, O, Ba, and Y nuclei), the theoretical predictions for the principal axis Vzz and the anisotropy parameter of the EFG tensor agree well with available experiments and the results of Ambrosch-Draxl et al. The principal axis at O sites are found to lie in the direction of the Cu-O dp bonding axis, and the oxygen values are largely determined by the internal anisotropy inside the oxygen spheres. This is consistent with the finding that the main contribution to the EFG at the Cu sites comes from the intrinsic quadrupole field provided by the nonspherical (internal) charge distributions surrounding each Cu atom arising from the strong anisotropic hybridization between Cu d and O p electrons. Surprisingly, the (Sternheimer antishielding) contribution from the core electrons mainly from the Cu 3p semicore electrons is found to be very small. Overall, the agreement of the oxygen EFG components themselves with experiment is good. The calculated Vzz values are within 20% of the experiment, except for Cu(2), which is only half of the observed value and results in a reversal of the relative magnitude of the EFG at Cu(1) and Cu(2) sites. This error may result from the inexact treatment of the 3p semicore states when they are allowed to relax and are described as band states. This is seen from the extreme sensitivity of the EFG to the calculated anisotropic charge distributions of the core electrons. Thus, a transfer of only 0.0014 electrons from Cu(2) 3px and 3py to 3pz would enhance the EFG value and produce perfect agreement with experiment.

Original languageEnglish
Pages (from-to)532-541
Number of pages10
JournalPhysical Review B
Volume43
Issue number1
DOIs
Publication statusPublished - 1991

Fingerprint

High temperature superconductors
high temperature superconductors
Electric fields
gradients
electric fields
Electrons
Charge distribution
Oxygen
electrons
charge distribution
Anisotropy
oxygen
Experiments
anisotropy
barium copper yttrium oxide
Superconducting materials
Tensors
plane waves
quadrupoles
tensors

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Origin of electric-field gradients in high-temperature superconductors : YBa2Cu3O7. / Yu, Jaejun; Freeman, Arthur J; Podloucky, R.; Herzig, P.; Weinberger, P.

In: Physical Review B, Vol. 43, No. 1, 1991, p. 532-541.

Research output: Contribution to journalArticle

Yu, Jaejun ; Freeman, Arthur J ; Podloucky, R. ; Herzig, P. ; Weinberger, P. / Origin of electric-field gradients in high-temperature superconductors : YBa2Cu3O7. In: Physical Review B. 1991 ; Vol. 43, No. 1. pp. 532-541.
@article{952be2c12566431d9a7267e00c18eace,
title = "Origin of electric-field gradients in high-temperature superconductors: YBa2Cu3O7",
abstract = "The origin of the electric-field gradients (EFG) at nuclear sites in the high-Tc superconductor YBa2Cu3O7 is investigated theoretically by means of highly precise local-density full-potential linearized-augmented-plane-wave calculations. In all cases considered (i.e., at Cu, O, Ba, and Y nuclei), the theoretical predictions for the principal axis Vzz and the anisotropy parameter of the EFG tensor agree well with available experiments and the results of Ambrosch-Draxl et al. The principal axis at O sites are found to lie in the direction of the Cu-O dp bonding axis, and the oxygen values are largely determined by the internal anisotropy inside the oxygen spheres. This is consistent with the finding that the main contribution to the EFG at the Cu sites comes from the intrinsic quadrupole field provided by the nonspherical (internal) charge distributions surrounding each Cu atom arising from the strong anisotropic hybridization between Cu d and O p electrons. Surprisingly, the (Sternheimer antishielding) contribution from the core electrons mainly from the Cu 3p semicore electrons is found to be very small. Overall, the agreement of the oxygen EFG components themselves with experiment is good. The calculated Vzz values are within 20{\%} of the experiment, except for Cu(2), which is only half of the observed value and results in a reversal of the relative magnitude of the EFG at Cu(1) and Cu(2) sites. This error may result from the inexact treatment of the 3p semicore states when they are allowed to relax and are described as band states. This is seen from the extreme sensitivity of the EFG to the calculated anisotropic charge distributions of the core electrons. Thus, a transfer of only 0.0014 electrons from Cu(2) 3px and 3py to 3pz would enhance the EFG value and produce perfect agreement with experiment.",
author = "Jaejun Yu and Freeman, {Arthur J} and R. Podloucky and P. Herzig and P. Weinberger",
year = "1991",
doi = "10.1103/PhysRevB.43.532",
language = "English",
volume = "43",
pages = "532--541",
journal = "Physical Review B-Condensed Matter",
issn = "1098-0121",
publisher = "American Physical Society",
number = "1",

}

TY - JOUR

T1 - Origin of electric-field gradients in high-temperature superconductors

T2 - YBa2Cu3O7

AU - Yu, Jaejun

AU - Freeman, Arthur J

AU - Podloucky, R.

AU - Herzig, P.

AU - Weinberger, P.

PY - 1991

Y1 - 1991

N2 - The origin of the electric-field gradients (EFG) at nuclear sites in the high-Tc superconductor YBa2Cu3O7 is investigated theoretically by means of highly precise local-density full-potential linearized-augmented-plane-wave calculations. In all cases considered (i.e., at Cu, O, Ba, and Y nuclei), the theoretical predictions for the principal axis Vzz and the anisotropy parameter of the EFG tensor agree well with available experiments and the results of Ambrosch-Draxl et al. The principal axis at O sites are found to lie in the direction of the Cu-O dp bonding axis, and the oxygen values are largely determined by the internal anisotropy inside the oxygen spheres. This is consistent with the finding that the main contribution to the EFG at the Cu sites comes from the intrinsic quadrupole field provided by the nonspherical (internal) charge distributions surrounding each Cu atom arising from the strong anisotropic hybridization between Cu d and O p electrons. Surprisingly, the (Sternheimer antishielding) contribution from the core electrons mainly from the Cu 3p semicore electrons is found to be very small. Overall, the agreement of the oxygen EFG components themselves with experiment is good. The calculated Vzz values are within 20% of the experiment, except for Cu(2), which is only half of the observed value and results in a reversal of the relative magnitude of the EFG at Cu(1) and Cu(2) sites. This error may result from the inexact treatment of the 3p semicore states when they are allowed to relax and are described as band states. This is seen from the extreme sensitivity of the EFG to the calculated anisotropic charge distributions of the core electrons. Thus, a transfer of only 0.0014 electrons from Cu(2) 3px and 3py to 3pz would enhance the EFG value and produce perfect agreement with experiment.

AB - The origin of the electric-field gradients (EFG) at nuclear sites in the high-Tc superconductor YBa2Cu3O7 is investigated theoretically by means of highly precise local-density full-potential linearized-augmented-plane-wave calculations. In all cases considered (i.e., at Cu, O, Ba, and Y nuclei), the theoretical predictions for the principal axis Vzz and the anisotropy parameter of the EFG tensor agree well with available experiments and the results of Ambrosch-Draxl et al. The principal axis at O sites are found to lie in the direction of the Cu-O dp bonding axis, and the oxygen values are largely determined by the internal anisotropy inside the oxygen spheres. This is consistent with the finding that the main contribution to the EFG at the Cu sites comes from the intrinsic quadrupole field provided by the nonspherical (internal) charge distributions surrounding each Cu atom arising from the strong anisotropic hybridization between Cu d and O p electrons. Surprisingly, the (Sternheimer antishielding) contribution from the core electrons mainly from the Cu 3p semicore electrons is found to be very small. Overall, the agreement of the oxygen EFG components themselves with experiment is good. The calculated Vzz values are within 20% of the experiment, except for Cu(2), which is only half of the observed value and results in a reversal of the relative magnitude of the EFG at Cu(1) and Cu(2) sites. This error may result from the inexact treatment of the 3p semicore states when they are allowed to relax and are described as band states. This is seen from the extreme sensitivity of the EFG to the calculated anisotropic charge distributions of the core electrons. Thus, a transfer of only 0.0014 electrons from Cu(2) 3px and 3py to 3pz would enhance the EFG value and produce perfect agreement with experiment.

UR - http://www.scopus.com/inward/record.url?scp=0000252322&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000252322&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.43.532

DO - 10.1103/PhysRevB.43.532

M3 - Article

VL - 43

SP - 532

EP - 541

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 1098-0121

IS - 1

ER -