Symmetry of the free states of an electron-doped Nd2−xCexCuO4−δ superconductor determined by x-ray-absorption spectroscopy
A. Yu. Ignatov, A. A. Ivanov, A. P. Menushenkov, S. Iacobucci, P. Lagarde
DOI 10.1103/PhysRevB.57.8671 · Physical Review B
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Abstract
Polarization-dependent x-ray-absorption spectroscopy at the Cu L3 and Ce M4,5 edges has been performed on epitaxial films of Nd1.85Ce0.15CuO4−δ vs defect concentration induced by He+ ion irradiation. The Cu L3 edge exhibits an increase in the integral intensity of both the white line in E∥ab (∼15%) and the first peak in E∥c (∼20%) after superconductivity suppression. At the same time, partial filling of Ce 4f orbitals (∼16%) takes place, though the shape of Ce M4,5 edges remains the same as for the formally tetravalent Ce ion. The mechanism of superconductivity suppression in Nd1.85Ce0.15CuO4−δ under He+ ion irradiation is discussed. The Cu L3-edge measurements vs Ce doping indicate that the major part (∼70%) of the excess electrons fill Cu 3dx2−y2 states in Nd1.85Ce0.15CuO4−δ. The remaining part extends beyond the CuO2 superconducting plane forming “impurity” states that seem to be localized within a few unit cells.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Nd1.85Ce0.15CuO4 Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 21 | Pressure not reported | onset |
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