Effects of electronic correlations and disorder on the thermopower of NaxCoO2

Abstract

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.

23 pages, 27 figures, accepted at PRB

References in corpus (8)

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• ARPES on Na${}_{0.6}$CoO${}_2$: Fermi surface, extended flat dispersion, and unusual band splitting
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• Electronic thermal transport in strongly correlated multilayered nanostructures
• Coulomb correlations do not fill the e'_g hole pockets in Na_{0.3}CoO_2

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• Pudding-mold type band in a potential thermoelectric material CuAlO${}_2$ : comparison with Na${}_x$CoO${}_2$
• Correlated electronic structure with uncorrelated disorder
• Ferrimagnetic ordering and spin entropy of field-dependent intermediate spins in Na0.82CoO2
• Thermopower of the electron-doped manganese pnictide LaMnAsO
• Enhancement of the effective disorder potential and the thermopower in Na${}_x$CoO${}_2$ through the electron-phonon coupling
• Effects of lattice geometry on thermopower properties of the repulsive Hubbard model
• Enhanced low energy fluctuations and increasing out-of-plane coherence in vacancy ordered NaxCoO2