Hole distribution in (Tl{sub 0.5}Pb{sub 0.5})Sr{sub 2}(Ca{sub 1{minus}{ital x}}Y{sub {ital x}})Cu{sub 2}O{sub 7} studied by x-ray absorption spectroscopy
- Synchrotron Radiation Research Center (SRRC), Hsinchu, Taiwan, Republic of (China)
- Department of Chemistry, National Taiwan University, Taipei, Taiwan, Republic of (China)
- Interdisciplinary Research Center in Superconductivity, University of Cambridge, Cambridge (United Kingdom)
High-resolution O {ital K}-edge and Cu {ital L}{sub 23}-edge x-ray-absorption near-edge-structure spectra for the series of (Tl{sub 0.5}Pb{sub 0.5})Sr{sub 2}(Ca{sub 1{minus}{ital x}}Y{sub {ital x}})Cu{sub 2}O{sub 7} compounds ({ital x}=0{endash}0.9) were measured using a bulk-sensitive total-fluorescence-yield technique. Near the O 1{ital s} edge, a well-pronounced pre-edge peak with maxima at {approximately}528.3 eV is observed, which is ascribed to the excitations of O 1{ital s} electrons to O 2{ital p} holes located in the CuO{sub 2} planes. The intensity of this pre-edge peak increases linearly with the Ca doping for 0{le}{ital x}{le}0.5. This indicates that the effect of chemical substitution of Ca{sup 2+} for Y{sup 3+} is to induce hole states in the CuO{sub 2} planes near the Fermi level, which are important to control the {ital T}{sub {ital c}} for the series of (Tl{sub 0.5}Pb{sub 0.5})Sr{sub 2}(Ca{sub 1{minus}{ital x}}Y{sub {ital x}})Cu{sub 2}O{sub 7} compounds. Moreover, the generation of holes in the O 2{ital p} orbitals within the CuO{sub 2} planes is probably responsible for inducing a transition from a semiconductor to a superconductor. In the Cu {ital L}-edge absorption spectra, high-energy shoulders at 933.1 and 952.9 eV are assigned to the transitions from the Cu(2{ital p}{sub 3/2,1/2})3{ital d}{sup 9}{ital L} ground state to the Cu(2{ital p}{sub 3/2,1/2}){sup {minus}1}3{ital d}{sup 10}{ital L} excited state, where {ital L} denotes the O 2{ital p} ligand hole. The normalized intensity of these defect states shows a linear increase with increasing the chemical concentration of Ca in the Y sites. {copyright} {ital 1996 The American Physical Society.}
- OSTI ID:
- 388343
- Journal Information:
- Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 17 Vol. 54; ISSN 0163-1829; ISSN PRBMDO
- Country of Publication:
- United States
- Language:
- English
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