Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.54: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

Orbital responses in 3d¹ perovskite titanates — •Luis Craco — Max-Planck Institute for Chemical Physics of Solids, Noethnitzer Str. 40, D-01187 Dresden, Germany

LaTiO₃ and YTiO₃ have long been considered as classic examples of systems where the change of electron correlations originates form a change in the 3d electron hopping, which is governed by the Ti-O bond angles. Using a combination of ab initio and correlated many-body treatments, we consider the role of lattice distortions and multi-orbital electron interactions in these classical 3d¹ perovskites. We show how the Mott-Hubbard insulating state is affected by structural distortions and the concomitant orbital polarization pattern. For this we use the LDA+DMFT method, which combines the real one-electron band structure with dynamical effects of strong, electron interactions. Our band-structure results are consistent with a removal of the t_2g and e_g orbital degeneracy due to orthorhombic distortions. In this real band-structure, we show that the Mott insulating state is driven by strong electron interactions. The obtained correlated spectra shows good agreement with experiments (photo-emission and/or optics). We find that La(Y)TiO₃ are described as orbitally non-degenerate systems, where multi-orbital correlations, orbital polarization and disorder are very important in determining the nature of the paramagnetic insulating state. As an extension of our work, we plan to describe the (ferromagnetic) ground-state properties of YTiO₃ and the effect of pressure in the system.