Dresden 2009 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 9: Correlated Electrons: Metal-Insulator Transition 1

TT 9.9: Vortrag

Montag, 23. März 2009, 16:15–16:30, HSZ 03

On the mechanism for orbital-ordering in KCuF₃ — •Eva Pavarini¹, Erik Koch¹, and Alexander I. Lichtenstein² — ¹Institut für Festkörperforschung and Institute for Advanced Simulations, Forschungzentrum Juelich — ²Institute of Theoretical Physics, University of Hamburg

The Mott insulating perovskite KCuF₃ is considered the archetype of an orbitally-ordered system. By using the LDA+dynamical mean-field theory (DMFT) method, we investigate the mechanism for orbital-ordering (OO) in this material. We show that the purely electronic Kugel-Khomskii super-exchange mechanism (KK) alone leads to a remarkably large transition temperature of T_KK∼ 350 K. However, orbital-order is experimentally believed to persist to at least 800 K. Thus Jahn-Teller distortions are essential for stabilizing orbital-order at such high temperatures.