Localized and mixed valence state of Ce $4f$ in superconducting and ferromagnetic CeO${}_{1-x}$F${}_x$BiS${}_2$ revealed by x-ray absorption and photoemission spectroscopy

Abstract

We have performed Ce $L_3$-edge x-ray absorption spectroscopy (XAS) and Ce $4d$-$4f$ resonant photoemission spectroscopy (PES) on single crystals of CeO${}_{1-x}$F${}_x$BiS${}_2$ for $x=0.0$ and 0.5 in order to investigate the Ce $4f$ electronic states. In the Ce $L_3$-edge XAS, mixed valence of Ce was found in the $x=0.0$ sample and the F-doping suppresses it, which is consistent with the results on polycrystalline samples. As for the resonant PES, we found that the Ce $4f$ electrons in both $x=0.0$ and $0.5$ systems respectively form a flat band at 1.0 eV and 1.4 eV below the Fermi level and there is no contribution to the Fermi surfaces. Interestingly, Ce valence in CeOBiS${}_2$ deviates from Ce${}^{3+}$ 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 CeOBiS${}_2$ is mixed with the unoccupied Bi $6p_z$, which is consistent with the previous local structural study. Based on the analysis of the Ce $L_3$-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.

arXiv comment5 pages, 3 figures

References in corpus (22)

• Novel BiS2-based layered superconductor Bi4O4S3
• Superconductivity Appears in the Vicinity of an Insulating-Like Behavior in CeO${}_{1-x}$F${}_x$BiS${}_2$
• Superconductivity of F-substituted LnOBiS2 (Ln = La, Ce, Pr, Nd, Yb) compounds
• Ferroelectric Soft Phonons, Charge Density Wave Instability and Strong Electron-Phonon Coupling in BiS2-Layered Superconductors
• Pressure Study of BiS2-Based Superconductors Bi4O4S3 and La(O,F)BiS2
• Density-functional calculations of the electronic structure and lattice dynamics of superconducting LaO${}_{0.5}$F${}_{0.5}$BiS${}_2$: Evidence for an electron-phonon interaction near the charge-density-wave instability
• Superconductivity induced by electron doping in the system La1-xMxOBiS2 (M = Ti, Zr, Hf, Th)
• Evolution of superconductivity in LaO1-xFxBiS2 prepared by high pressure technique
• Appearance of superconductivity in new BiS2 based layered LaO0.5F0.5BiS2
• Electronic structure and superconductivity of BiS2-based compounds LaO1-xFxBiS2
• Superconductivity at 5K in NdO0.5F0.5BiS2
• Growth and superconducting properties of F-substituted ROBiS2 (R = La, Ce, Nd) single crystals
• Coexistence of bulk superconductivity and ferromagnetism in CeO1-xFxBiS2
• Role of the Ce valence in the coexistence of superconductivity and ferromagnetism of CeO${}_{1-x}$F${}_x$BiS${}_2$ revealed by Ce $L_3$-edge x-ray absorption spectroscopy
• Crystal Structure, Lattice Vibrations, and Superconductivity of LaO${}_{1-x}$F${}_x$BiS${}_2$
• Electronic Structure of Single Crystalline NdO${}_{0.5}$F${}_{0.5}$BiS${}_2$ Studied by Angle-resolved Photoemission Spectroscopy
• s-wave pairing in the optimally-doped LaO0.5F0.5BiS2 superconductor
• Pairing Symmetry in Layered BiS${}_2$ Compounds Driven by Electron-Electron Correlation
• Observation of anomalous temperature dependence of spectrum on small Fermi surfaces in a BiS2-based superconductor
• Fermi surfaces and orbital polarization in superconducting CeO${}_{0.5}$F${}_{0.5}$BiS${}_2$ revealed by angle-resolved photoemission spectroscopy
• Pronounced - Log T Divergence in Specific Heat of Nonmetallic CeOBiS${}_2$: A Mother Phase of BiS${}_2$-Based Superconductor
• Electronic and magnetic properties of superconducting LnO${}_{1-x}$F${}_x$BiS${}_2$ (Ln = La, Ce, Pr, and Nd) from first principles

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• Superconductivity in La1-xCexOBiSSe: carrier doping by mixed valence of Ce ions
• Two-Dimensional Phase-Fluctuating Superconductivity in Bulk-Crystalline NdO${}_{0.5}$F${}_{0.5}$BiS${}_2$