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TT: Fachverband Tiefe Temperaturen

TT 28: CE: (General) Theory 2

TT 28.1: Talk

Tuesday, March 15, 2011, 14:00–14:15, HSZ 105

Enhancement of the Na_xCoO₂ thermopower due to electronic correlations — •Karsten Held, Philipp Wissgott, and Alessandro Toschi — Institute for Solid State Physics, TU Wien

Climate change and the prospective oil peak necessitate the discovery of new green energy sources. One possibility in this context is to convert hithero unused excess heat into electrical energy using thermoelectrics. For a real breakthrough and a widespread application of this technology however, better materials are needed. 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 bandstructure and correlation engineering may lead to a substantial increase of the thermoelectric figure of merit.