Anisotropy and oxygen-stoichiometry dependence of the dielectric tensor ofYBa2Cu3O7−δ(0≤δ≤1)
| Autor: | Manuel Cardona, D. Fuchs, S Rashkeev, M. K. Kelly, Mebarek Alouani, J. Kircher |
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| Rok vydání: | 1991 |
| Předmět: | |
| Zdroj: | Physical Review B. 44:217-224 |
| ISSN: | 1095-3795 0163-1829 |
| DOI: | 10.1103/physrevb.44.217 |
| Popis: | The dielectric tensor elements of oriented YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} samples, as obtained by spectroscopic ellipsometry, are presented for several oxygen stoichiometries in the photon energy range between 1.66 and 5.5 eV. For {delta}=0 and 1, we extend this range up to 9.5 eV using a recently developed synchrotron radiation ellipsometer. We compare the experimental results with computed values for the dielectric function obtained from a linear-muffin-tin-orbitals band-structure calculation. We find good general agreement for both the orientational and compositional dependence. In particular, both experiment and theory show {ital c} polarization for a peak near 2.7 eV for {delta}{lt}0.5, while a transition in that spectral region is {ital a} polarized for YBa{sub 2}Cu{sub 3}O{sub 6}. In spite of the difficulty in predicting insulating behavior of the low-oxygen material, these results show that the local-density-approximation picture is successful in describing much of the electronic structure determining higher-energy excitations. In addition, the measured dependence of the dielectric tensor on the oxygen stoiochiometry provides a reference for optical determination of the oxygen content and orientation in applications, such as thin-film or single-crystal growth. |
| Databáze: | OpenAIRE |
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