Berlin 2012 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 39: Focussed session: Frontiers of electronic structure theory: Strong correlations from first principles III (jointly with TT)
O 39.1: Vortrag
Mittwoch, 28. März 2012, 10:30–10:45, HE 101
Reduced effective spin-orbital degeneracy and spin-orbital ordering in paramagnetic transition metal oxides:
Sr2IrO4 vs. Sr2RhO4 — •Cyril Martins1,2, Markus Aichhorn1,3, Loïg Vaugier1, and Silke Biermann1,2 — 1Centre de Physique Théorique, Ecole Polytechnique, CNRS, 91128 Palaiseau Cedex, France. — 2Japan Science and Technology Agency, CREST, Kawaguchi 332-0012, Japan. — 3Institute of Theoretical and Computational Physics, TU Graz, Petersgasse 16, Graz, Austria.
We discuss the notions of spin-orbital polarization and ordering in paramagnetic materials, and address their consequences in transition metal oxides. Extending the combined density functional and dynamical mean field theory scheme to the case of materials with large spin-orbit interactions, we investigate the electronic excitations of the paramagnetic phases of Sr2IrO4 and Sr2RhO4. We show that the interplay of spin-orbit interactions, structural distortions and Coulomb interactions suppresses spin-orbital fluctuations. As a result, the room temperature phase of Sr2IrO4 is a paramagnetic spin-orbitally ordered Mott insulator. In Sr2RhO4, the effective spin-orbital degeneracy is reduced, but the material remains metallic, due to both, smaller spin-orbit and smaller Coulomb interactions. We find excellent agreement of our ab-initio calculations for Sr2RhO4 with angle-resolved photoemission, and make predictions for spectra of the paramagnetic phase of Sr2IrO4.