paper

Cooperative Jahn-Teller Effect and Electron-Phonon Coupling in

arXiv:cond-mat/9510147 · doi:10.1103/PhysRevB.53.8434

Abstract

A classical model for the lattice distortions of $\lax$ is derived and, in a mean field approximation, solved. The model is based on previous work by Kanamori and involves localized Mn d-electrons (which induce tetragonal distortions of the oxygen octahedra surrounding the Mn) and localized holes (which induce breathing distortions). Parameters are determined by fitting to the room temperature structure of . The energy gained by formation of a local lattice distortion is found to be large, most likely eV per site, implying a strong electorn-phonon coupling and supporting polaronic models of transport in the doped materials. The structural transition is shown to be of the order-disorder type; the rapid x-dependence of the transition temperature is argued to occur because added holes produce a "random" field which misaligns the nearby sites.

24 pages. No figures. One Table. Latex

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