On the mechanism for orbital-ordering in KCuF3
E. Pavarini, E. Koch, A. I. Lichtenstein
TL;DR
This paper investigates the orbital-ordering mechanism in KCuF3 using LDA+DMFT, revealing that electronic super-exchange alone cannot explain the high-temperature orbital-order, emphasizing the importance of Jahn-Teller distortions.
Contribution
The study demonstrates that purely electronic super-exchange mechanisms cannot account for the high orbital-ordering temperature, highlighting the role of Jahn-Teller distortions in KCuF3.
Findings
Super-exchange mechanism predicts a transition temperature of about 350 K.
Experimental orbital-order persists up to at least 800 K.
Jahn-Teller distortions are crucial for stabilizing high-temperature orbital-order.
Abstract
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 about 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.
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