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Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 19: CE: Metal-Insulator Transition 2

TT 19.5: Talk

Wednesday, March 24, 2010, 10:30–10:45, H18

Origin of Jahn-Teller distortion and orbital-order in LaMnO3 — •Eva Pavarini1 and Erik Koch21IFF und IAS, Forschungszentrum Jülich — 2GRS, Jülich

The origin of the cooperative Jahn-Teller distortion and orbital-order in LaMnO3 is central to the physics of the manganites. The question is complicated by the simultaneous presence of tetragonal and GdFeO3-type distortions and the strong Hund’s rule coupling between eg and t2g electrons. To clarify the situation we calculate the transition temperature for the Kugel-Khomskii superexchange mechanism by using the local density approximation+dynamical mean-field method, and disentangle the effects of super-exchange from those of lattice distortions. We find that super-exchange alone would yield TKK∼650 K. The tetragonal and GdFeO3-type distortions, however, reduce TKK to ∼ 550 K. Thus electron-phonon coupling is essential to explain the persistence of local Jahn-Teller distortions to 1150 K and to reproduce the occupied orbital deduced from neutron scattering.

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