Investigating thermoelectricity in maerials with different strength of electronic correlations

• Antragsteller: Professor Dr. Hanns-Ulrich Habermeier; Dr. Frank Lechermann
• Fachliche Zuordnung: Experimentelle Physik der kondensierten Materie
• Förderung: Förderung von 2009 bis 2013
• Projektkennung: Deutsche Forschungsgemeinschaft (DFG) - Projektnummer 120485794

The nanostructuring of weakly-to-moderately correlated thermoelectric materials has proven in recent years to largely enhance the respective figure of merit. Thus the key focus in the second funding period of the present project is to investigate the same structering issue in the context of strongly correlated materials, namely selected transition-metal oxides such as cobaltates, manganites, ferrates, etc. . We will study, both theoretically as well as experimentally, thin-films and heterostructures as well as on the experimental side even more complicated morphologies. Especially the influence of a given surface will be examined in theoretical detail, since the phenomena elucidated there may apply to various geometries. Studying heterostructures and multi-layers will allow for the description of emergent transport properties when bringing different materials systems in direct contact. Further advanced superlattice geometries for the given materials will challenge the band-theory concept in the presence of strong electronic correlations. The theoretical modeling will benefit from recent development within the framework of LDA+DMFT in combination with a transport approach building up un the generic Kubo formalism. This allows to go beyond the constant-relaxation time approximation for the Boltzmannequation approach and can deal with e.g. the realistic temperature effects, i. e. the correct description of the flow of electronic entropy. Contact will be made with thermal transport measurements within other projects in the main project.Furthermore the effect of spin-orbit coupling on the thermoelectricity of higher 4d/5d transition-metal oxides will be an additional point of interest in our research effort. The important competition between the complexity enhancement of the band structure and the increased quenching of spin fluctuations in the presence of the spin-orbit interaction deserves deeper studies in order to possibly open the the door for thermoelectricity research in the regime of heavier elements aside from the well-known weakly correlates systems, such as e.g. Bi2Te3.

• DFG-Verfahren: Schwerpunktprogramme
• Teilprojekt zu: SPP 1386: Nanostrukturierte Thermoelektrika: Theorie, Modellsysteme und kontrollierte Synthese
• Beteiligte Person: Professor Dr. Alexander Lichtenstein