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Effects of electronic correlations and disorder on the thermopower of NaxCoO2

  • Wissgott, Philipp
  • Toschi, Alessandro
  • Sangiovanni, Giorgio
  • Held, Karsten
Published Article
Publication Date
May 19, 2011
Submission Date
May 19, 2011
DOI: 10.1103/PhysRevB.84.085129
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For the thermoelectric properties of NaxCoO2, we analyze the effect of local Coulomb interaction and (disordered) potential differences for Co-sites with adjacent Na-ion or vacancy. The disorder potential alone increases the resistivity and reduces the thermopower, while the Coulomb interaction alone leads only to minor changes compared to the one-particle picture of the local density approximation. Only combined, these two terms give rise to a substantial increase of the thermopower: the number of (quasi-)electrons around the Fermi level is much more suppressed than that of the (quasi-)holes. Hence, there is a particle-hole imbalance acting in the same direction as a similar imbalance for the group velocities. Together, this interplay results in a large positive thermopower. Introducing a thermoelectric spectral density, we located the energies and momenta regions most relevant for the thermopower and changes thereof.

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