Hole distribution in (Tl0.5Pb0.5)Sr-2(Ca1-xYx)Cu2O7 studied by x-ray absorption spectroscopy
Journal
Physical Review B
Journal Volume
54
Journal Issue
17
Pages
12587-12593
Date Issued
1996
Author(s)
Abstract
High-resolution O K-edge and Cu (Formula presented)-edge x-ray-absorption near-edge-structure spectra for the series of ((Formula presented)(Formula presented))(Formula presented)((Formula presented)(Formula presented))(Formula presented)(Formula presented) compounds (x=0-0.9) were measured using a bulk-sensitive total-fluorescence-yield technique. Near the O 1s edge, a well-pronounced pre-edge peak with maxima at ∼528.3 eV is observed, which is ascribed to the excitations of O 1s electrons to O 2p holes located in the (Formula presented) planes. The intensity of this pre-edge peak increases linearly with the Ca doping for 0≤x≤0.5. This indicates that the effect of chemical substitution of (Formula presented) for (Formula presented) is to induce hole states in the (Formula presented) planes near the Fermi level, which are important to control the (Formula presented) for the series of ((Formula presented)(Formula presented))(Formula presented)((Formula presented)(Formula presented))(Formula presented)(Formula presented) compounds. Moreover, the generation of holes in the O 2p orbitals within the (Formula presented) planes is probably responsible for inducing a transition from a semiconductor to a superconductor. In the Cu L-edge absorption spectra, high-energy shoulders at 933.1 and 952.9 eV are assigned to the transitions from the Cu(2(Formula presented))3(Formula presented)L ground state to the Cu(2(Formula presented)(Formula presented)3(Formula presented)L excited state, where L denotes the O 2p ligand hole. The normalized intensity of these defect states shows a linear increase with increasing the chemical concentration of Ca in the Y sites. © 1996 The American Physical Society.
Type
journal article