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Fermi surface evolution and Luttinger theorem in Na$_x$CoO$_2$: a systematic photoemission study

H. -B. Yang·Z. -H. Pan·A. K. P. Sekharan·T. Sato·S. Souma·T. Takahashi·R. Jin·B. C. Sales·D. Mandrus·A. V. Fedorov·Z. Wang·H. Ding
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Abstract

We report a systematic angle-resolved photoemission study on Na$_x$CoO$_2$ for a wide range of Na concentrations ($0.3 \leq x \leq 0.72$). In all the metallic samples at different $x$, we observed (i) only a single hole-like Fermi surface centered around $Γ$ and (ii) its area changes with $x$ according to the Luttinger theorem. We also observed a surface state that exhibits a larger Fermi surface area. The $e_g^\prime$ band and the associated small Fermi surface pockets near the $K$ points predicted by band calculations are found to ``sink'' below the Fermi energy in a manner almost independent of the doping and temperature.

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H. -B. Yang, Z. -H. Pan, A. K. P. Sekharan, T. Sato, S. Souma, T. Takahashi, R. Jin, B. C. Sales, D. Mandrus, A. V. Fedorov, Z. Wang, H. Ding. 2005-01-17. Fermi surface evolution and Luttinger theorem in Na$_x$CoO$_2$: a systematic photoemission study. https://doi.org/10.1103/physrevlett.95.146401

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