Dresden 2014 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
TT: Fachverband Tiefe Temperaturen
TT 86: Correlated Electrons: Other Materials
TT 86.6: Talk
Thursday, April 3, 2014, 10:45–11:00, BEY 81
On the orbital-ordering transition in KCuF3 — •Hunter Sims1, Eva Pavarini2, and Erik Koch1 — 1German Research School for Simulation Sciences, 52428 Jülich, Germany — 2Institute for Advanced Simulation, Forschungszentrum Jülich, 52428 Jülich, Germany
The Mott insulating perovskite KCuF3 is considered the paradigmatic system with long-ranged orbital order and a cooperative Jahn-Teller distortion of the F-octahedra. This broken symmetry state is usually understood as the result of the destabilization of the symmetric structure due to crystal-field splitting (Jahn-Teller effect) or to super-exchange between the orbitals (Kugel-Khomskii mechanism), which leads to a gain in energy with increasing distortion. This is counteracted by the quadratic deformation energy of the lattice. In this picture it is expected that, as a consequence of the lattice entropy, the distortions will be gradually reduced with increasing temperature until they finally vanish at the ordering temperature Tc. Such a transition is, however, not found experimentally. We explain why.