TY - JOUR
T1 - Localized and mixed valence state of Ce 4f in superconducting and ferromagnetic CeO1-x FxBiS2 revealed by x-ray absorption and photoemission spectroscopy
AU - Sugimoto, T.
AU - Ootsuki, D.
AU - Paris, E.
AU - Iadecola, A.
AU - Salome, M.
AU - Schwier, E. F.
AU - Iwasawa, H.
AU - Shimada, K.
AU - Asano, T.
AU - Higashinaka, R.
AU - Matsuda, T. D.
AU - Aoki, Y.
AU - Saini, N. L.
AU - Mizokawa, T.
N1 - Funding Information:
The authors are grateful to M. Zheng and Y. Kojima for their support during the experimental run at BL-1, Hiroshima Synchrotron Radiation Center. T.S. and D.O. acknowledge support from a JSPS Research Fellowship for Young Scientists. This work is partly supported by JSPS KAKENHI (Grants No. 15H03693 and No. 25400356). E.F.S. acknowledges financial support from a JSPS postdoctoral fellowship for overseas researchers as well as the Alexander von Humboldt Foundation (Grant No. P13783). The synchrotron radiation experiments have been done with the approval of Hiroshima Synchrotron Radiation Center (Proposal No. 14-B-24).
Publisher Copyright:
©2016 American Physical Society.
PY - 2016/8/17
Y1 - 2016/8/17
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevB.94.081106
DO - 10.1103/PhysRevB.94.081106
M3 - Article
AN - SCOPUS:84985990095
VL - 94
JO - Physical Review B-Condensed Matter
JF - Physical Review B-Condensed Matter
SN - 2469-9950
IS - 8
M1 - 081106
ER -