Polarization dependence of x-ray absorption spectra in Na_xCoO_2

Abstract

In order to shed light on the electronic structure of Na_xCoO_2, and motivated by recent Co L-edge X-ray absorption spectra (XAS) experiments with polarized light, we calculate the electronic spectrum of a CoO_6 cluster including all interactions between 3d orbitals. We obtain the ground state for two electronic occupations in the cluster that correspond nominally to all O in the O^{-2} oxidation state, and Co^{+3} or Co^{+4}. Then, all excited states obtained by promotion of a Co 2p electron to a 3d electron, and the corresponding matrix elements are calculated. A fit of the observed experimental spectra is good and points out a large Co-O covalency and cubic crystal field effects, that result in low spin Co 3d configurations. Our results indicate that the effective hopping between different Co atoms plays a major role in determining the symmetry of the ground state in the lattice. Remaining quantitative discrepancies with the XAS experiments are expected to come from composition effects of itineracy in the ground and excited states.

arXiv comment10 pages, 4 figures

References in corpus (23)

• An Electronic Model for $Co{O}_2$ layer based systems: Chiral RVB metal and Superconductivity
• Fermi surface and quasiparticle dynamics of Na(x)CoO2 {x=0.7} investigated by Angle-Resolved Photoemission Spectroscopy
• Unconventional magnetic transition and transport behavior in Na0.75CoO2
• Coupling between electronic and structural degrees of freedom in the triangular lattice conductor NaxCoO2
• Doped t-J Model on a Triangular Lattice: Possible Application to Na${}_x$CoO${}_2\cdot y$H${}_2$0 and Na${}_{1-x}$TiO${}_2$
• Fermi surface evolution and Luttinger theorem in Na${}_x$CoO${}_2$: a systematic photoemission study
• ARPES on Na${}_{0.6}$CoO${}_2$: Fermi surface, extended flat dispersion, and unusual band splitting
• Quantum Critical Behavior and Possible Triplet Superconductivity in Electron Doped CoO2 Sheets
• Bulk antiferromagnetism in $\mathbf{N}{\mathbf{a}}_{0.82}\mathbf{Co}{\mathbf{O}}_2$ single crystals
• Impurity-induced transition and impurity-enhanced thermopower in the thermoelectric oxide NaCo_{2-x}Cu_x$O_4
• Orbital Symmetry and Electron Correlation in Na_{x}CoO_2
• Evidence of a single nonmagnetic Co3+ state in the Na1CoO2 cobaltate
• Low energy electronic states and triplet pairing in layered cobaltates
• Bulk Electronic structure of Na${}_{0.35}$CoO${}_2$.1.3H${}_2$O
• Optical properties of an effective one-band Hubbard model for the cuprates
• Excitons in insulating cuprates
• X-ray absorption spectroscopy on layered cobaltates Na_xCoO_2
• Superconductivity and incommensurate spin fluctuations in a generalized t-J model for the cuprates
• Spin dynamics of hole doped Y2BaNiO5
• Quasiparticle photoemission intensity in doped two-dimensional quantum antiferromagnets
• Magnetic and orbital ordering of RuO2 planes in RuSr2(Eu,Gd)Cu2O8
• Angle resolved Cu and O photoemission intensities in CuO_2 planes
• Effective three-band model for double perovskites

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• Dynamical mean field theory of an effective three-band model for Na${}_x$CoO${}_2$
• Electronic structure and Fermi surface tolopogy of Na${}_x$CoO${}_2$
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• Evidence for Oxygen Holes due to d-p Rehybridization in Thermoelectric Sr_{1-x}Rh_{2}O_{4}
• A possibility of high spin hole states in doped CoO${}_2$ layered systems
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