Enhancement of the NaxCoO2 thermopower due to electronic correlations

Using the merger of local-density approximation and dynamical mean-field theory, we show how electronic correlations increase the thermopower of Na0.7CoO2 by 200%. The newly revealed mechanism is an asymmetric shift of (quasi) electrons and holes away from the Fermi level, concurrent with an asymmetry of the respective (group) velocities. Exploiting this effect in band structure and correlation engineering may lead to a substantial increase in the thermoelectric figure of merit.