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Spin entropy as the likely source of enhanced thermopower in $\rm\bf Na_xCo_2O_4

Yayu Wang·Nyrissa S. Rogado·R. J. Cava·N. P. Ong
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Abstract

In an electric field, the flow of electrons in a solid produces an entropy current in addition to the familiar charge current. This Peltier effect underlies all thermoelectric refrigerators. The upsurge in thermoelectric cooling applications has led to a search for more efficient Peltier materials and to renewed theoretical interest in how electron-electron interaction may enhance the thermopower $Q$ of materials such as the transition-metal oxides \cite{Mahan,Beni,Kotliar,Chaikin}. An important factor in this enhancement is the electronic spin entropy, which is predicted \cite{Chaikin,Kwak,KwakChaikin} to dominate the entropy current. Here we report evidence for such suppression in the layered oxide $\rm Na_xCo_2O_4$, and present evidence that it is a strong-correlation effect.

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Yayu Wang, Nyrissa S. Rogado, R. J. Cava, N. P. Ong. 2004-06-04. Spin entropy as the likely source of enhanced thermopower in $\rm\bf Na_xCo_2O_4. https://doi.org/10.1038/nature01639

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