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TT: Fachverband Tiefe Temperaturen

TT 40: Poster Session Correlated Electrons

TT 40.16: Poster

Mittwoch, 13. März 2013, 15:00–19:00, Poster D

Strong Spin-Orbital Coupling and Polarization as origin of the Insulating State in Sr₂IrO₄ — •Markus Aichhorn¹, Cyril Martins², Loig Vaugier², and Silke Biermann² — ¹Institut für theoretische Physik - Computational Physics, TU Graz, Austria — ²CPHT, Ecole Polytechnique, France

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 (DMFT) 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 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.