Temperature Dependence of the Chemical Potential in NaxCoO2: Implications for the Large Thermoelectric Power

Abstract

We have performed a temperature-dependent photoemission study of a NaxCoO2 (x~0.8) epitaxial thin film prepared by the reactive solid-phase epitaxy method. The chemical potential shift as a function of temperature was derived from the Co 3d peak shift, and revealed a crossover from the degenerate Fermion state at low temperatures to the correlated hopping state of Co3+/Co4+ mixed-valence at high temperatures. This suggests that the large thermoelectric power at high temperatures should be considered in the correlated hopping picture.

arXiv comment5 pages, 4 figures

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• Non-monotonic temperature dependence of thermopower in strongly correlated electron systems
• Chemical potential shift induced by double-exchange and polaronic effects in Nd_{1-x}Sr_xMnO_3
• Metal-nonmetal transition in LixCoO2 thin film and thermopower enhancement at high Li concentration
• Evidence for Oxygen Holes due to d-p Rehybridization in Thermoelectric Sr_{1-x}Rh_{2}O_{4}