Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 106: Complex Oxides: Bulk Properties, Surfaces and Interfaces (joint session TT/MA/KFM)

TT 106.4: Vortrag

Freitag, 16. März 2018, 10:15–10:30, H 0110

Thermoelectricity close to a metal-insulator transition in ultrathin LaNiO₃/LaAlO₃(001) superlattices — •Benjamin Geisler and Rossitza Pentcheva — Fakultät für Physik, Universität Duisburg-Essen, 47057 Duisburg, Germany

Transition metal oxides are a promising materials class for thermoelectric applications due to their chemical and thermal stability and environmental friendliness. Their thermoelectric response can be further improved by nanostructuring and reduced dimensionality. Here we explore the thermoelectric properties of (LaNiO₃)₁/(LaAlO₃)₁(001) superlattices near the confinement-induced metal-insulator transition by combining ab initio simulations including on-site Coulomb repulsion and Boltzmann theory. We find that the short-period vertical design strongly enhances the in-plane thermoelectricity owing to the Ni-site disproportionation, which is stabilized considerably by tensile epitaxial strain and octahedral tilting. The sensitivity of the system to epitaxial strain provides an additional parameter to optimize the thermoelectric performance. For a SrTiO₃(001) substrate, we predict room-temperature Seebeck coefficients and power factors that can compete with those of other oxide systems of current interest such as layered cobaltates. Comparison of the ultrathin superlattices with the metallic longer-period (LaNiO₃)₃/(LaAlO₃)₃(001) case establishes the metal-insulator transition as a crucial mechanism to obtain a high thermoelectric response.

Funding by the DFG within TRR 80 (G3 and G8) is acknowledged.