Photoemission on the highT c superconductors Y?Ba?Cu?O

Steiner, P.; Kinsinger, V.; Sander, I.; Siegwart, B.; Hüfner, S.; Politis, Constantinus

doi:10.1007/bf01307302

Cited by 160 publications

(23 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consistent with this, these authors note a shift of the main Cu 2p3/2 feature of 0.4 eV to higher binding energy between 100% Y and 0% Y doping levels in BiESr2Cal _ xYxCu208 + 8, corresponding to an estimated Cu valence change from 1.9 to 2.3 (Golden et al, 1991). A similar shift to high binding energy with increasing Cu valence is seen for YBaECU307 _ 8; here the formal copper valency is controlled by changing the oxygen content of the material (Gourieux et al, 1988;Flavell & Egdell, 1989;Dauth, Kachel, Rupp & Gudat, 1988;Herzog, Schwarz, Sixl & Hoppe, 1988;Steiner et al, 1987). However, a decrease in binding energy with increasing Cu valence is observed in Bi2SrECal-xYxCu208 + ~ by van Veenendaal et al and Itti et al (although the latter authors use a bondvalence-sum calculation to arrive at the conclusion that the reverse behaviour is expected) (van Veenendaal et al, 1993(van Veenendaal et al, , 1994Itti et al, 1991).…”

Section: Bi2sr2cal-xyxcu2oe÷6mentioning

confidence: 54%

Resonant Photoemission from Complex Cuprates and Nickelates

Flavell¹,

Hollingworth²,

Howlett³

et al. 1995

J Synchrotron Radiat

View full text Add to dashboard Cite

Synchrotron-excited resonant-photoemission measurements at rare-earth 4d ~ 4fand transition-metal 3p ~ 3d thresholds have been carried out using a variety of complex cuprates and nickelates on stations 6.1 (grazing-incidence monochromator) and 6.2 (toroidal-grating monochromator) at the SRS CLRC Daresbury Laboratory. The systems studied are Nd2Nil _xCuxO4, La2_xSrxNil _yFeyO4 + 6 and Bi2Sr/Cal_xYxCu208 + 6. A combination of EDC and constant-initial-state data is used to examine the 4f and 3d contributions to the valence-band density of states and their binding-energy positions relative to the Fermi energy. This allows the study of the valence states of the transitionmetal ions and their modulation on doping. For La2_ xSrxNii _ yFeyO4 + 6, this approach is used to infer a valence state of _> 3.0 for Fe. In the case of Bi2Sr2Cal _ xYxCuz08 + 6, the effect of Cu valence modulation on the 3p resonance is observed as x is varied. This is discussed in the light of controversy surrounding shifts in core-level photoemission with doping for this system.

show abstract

Section: Bi2sr2cal-xyxcu2oe÷6mentioning

confidence: 54%

Resonant Photoemission from Complex Cuprates and Nickelates

Flavell¹,

Hollingworth²,

Howlett³

et al. 1995

J Synchrotron Radiat

View full text Add to dashboard Cite

show abstract

“…In our opinion, the sets (A) and (B) may be considered as an upper and lower limit for the parameters which are appropriate to evaluate electron correlations in the ground state. We stress that they have to be distinguished from the effective parameters which enter the interpretation of, e.g., the photoemission experiments [5][6][7] and contain relaxation effects.…”

Section: Resultsmentioning

confidence: 99%

How strongly are electrons correlated in the high-Tc superconducting materials?

1987

View full text Add to dashboard Cite

Electron correlations within CuO 2 layers, a common structural unit in La-Ba-Cu-O and Y-Ba-Cu-O systems, are studied by using a tight-binding model Hamiltonian. It is found that electron correlations are particularly strong within Cu(3dx2 y2) orbitals. They do not only considerably suppress charge fluctuations, but also change the electron densities. As a consequence~ the average number of holes at Cu sites increases and local moments are formed. Our results agree qualitatively with the experimentally observed magnetic moments in the antiferromagnetic phase and support the point of view that these systems are similar to valence fluctuating systems.

show abstract

“…This suggests that Coulomb interactions within Cu(3dx2 y2) orbitals are large. This is also evident from the recent photoemission experiments [5][6][7] which show that the density of states at the Fermi level is small and that the d electron peak lies at lower energy than expected from band structure calculations. A nonmetallic behaviour of La2CuO 4 [8] also suggests that Hubbard U is large.…”

Section: Introductionmentioning

confidence: 56%

“…Since the discovery of high-T c superconducting oxides (HTSO) [1], there has been increasing evidence that electron correlations are sizeable in these materials [2][3][4][5][6][7][8]. Antiferromagnetic longrange order has been observed in La2CuO 4 [2,3].…”

Section: Introductionmentioning

confidence: 99%