Localized and mixed valence state of Ce 4f in superconducting and ferromagnetic CeO1-x FxBiS2 revealed by x-ray absorption and photoemission spectroscopy

T. Sugimoto, D. Ootsuki, E. Paris, A. Iadecola, M. Salome, E. F. Schwier, H. Iwasawa, K. Shimada, T. Asano, R. Higashinaka, T. D. Matsuda, Y. Aoki, N. L. Saini, T. Mizokawa

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14 Citations (Scopus)

Abstract

We have performed Ce L3-edge x-ray absorption spectroscopy (XAS) and Ce 4d-4f resonant photoemission spectroscopy (PES) on single crystals of CeO1-xFxBiS2 for x=0.0 and 0.5 in order to investigate the Ce 4f electronic states. In Ce L3-edge XAS, a mixed valence of Ce was found in the x=0.0 sample, and F doping suppressed it, which is consistent with the results on polycrystalline samples. As for resonant PES, we found that the Ce 4f electrons in both x=0.0 and 0.5 systems respectively formed a flat band at 1.0 and 1.4 eV below the Fermi level and there was no contribution to the Fermi surfaces. Interestingly, Ce valence in CeOBiS2 deviates from Ce3+ even though Ce 4f electrons are localized, indicating the Ce valence is not in a typical valence fluctuation regime. We assume that localized Ce 4f in CeOBiS2 is mixed with unoccupied Bi 6pz, which is consistent with a previous local structural study. Based on the analysis of the Ce L3-edge XAS spectra using Anderson's impurity model calculation, we found that the transfer integral becomes smaller, increasing the number of Ce 4f electrons upon the F substitution for O.

Original languageEnglish
Article number081106
JournalPhysical Review B
Volume94
Issue number8
DOIs
Publication statusPublished - 2016 Aug 17

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics

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