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Na Induced Correlations in Na$_x$CoO$_2$

C. A. Marianetti·G. Kotliar
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Abstract

Increasing experimental evidence is building which indicates that signatures of strong correlations are present in the Na rich region of Na$_x$CoO$_2$ (ie. $x\approx0.7$) and absent in the Na poor region (ie. $x\approx0.3$). This is unexpected given that NaCoO$_2$ is a band insulator and CoO$_2$ has an integer filled open shell making it a candidate for strong correlations. We explain these experimental observations by presenting a minimal low-energy Hamiltonian for the cobaltates and solving it within LDA+DMFT. The Na potential is shown to be a key element in understanding correlations in this material. Furthermore, LDA calculations for the realistic Na ordering predict a \emph{binary} perturbation of the Co sites which correlates with the Na$_1$ sites (ie. Na sites above/below Co sites).

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C. A. Marianetti, G. Kotliar. 2006-05-08. Na Induced Correlations in Na$_x$CoO$_2$. https://doi.org/10.1103/physrevlett.98.176405

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