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Using a combination of ab-initio and correlated many-body treatments,
we consider the role of multi-orbital electron interactions and GdFeO3
type in 3d1 perovskites LaTiO3 [1] and YTiO3 [2]. 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. The obtained
correlated spectra shows good agreement with experiments (PES, IPES
(for LaTiO3) and/or optics). We show that La(Y)TiO3 [1,2,3] are
orbitally non-degenerate systems, where multi-orbital correlations
and orbital polarization are very important in determining the nature
of the insulating state. Second, we discuss the effect of disorder in
these systems. Finally, motivated by recent work probing changes in
optical absorption across the paramagnetic-ferromagnetic transition
in YTiO3, we explore this issue within our LDA+DMFT scheme [4]. To
conclude, our work constitutes a first-principles correlation-based
attempt to address the outstanding issue of orbital-selective changes
in charge dynamics across the Mott transitions (with and without magnetic
order) in 3d1 perovskite titanates, and should be widely applicable to
other oxides of great interest showing orbital selective Mott transitions.
[1] L. Craco, M.S. Laad, S. Leoni, and E. Mueller-Hartmann, Phys. Rev. B 70, 195116 (2004). [2] L. Craco, S. Leoni, and E. Mueller-Hartmann, Phys. Rev. B. 74, 155128 (2006). [3] S. Leoni, L. Craco, A. Ormeci, and H. Rosner, Solid State Sciences 8, 1138 (2006). [4] L. Craco, S. Leoni, M.S. Laad, and H. Rosner, submited to PRL. |
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