Dynamic Jahn-Teller Effect and Distortional Disorder in Manganites

Abstract

We study the (local) dynamic Jahn-Teller (JT) effect in the context of a spin-andorbital t-J model for the manganites. It is shown that allowing the correlated e g electrons to form local vibronic states with variationally optimized distortion amplitude, leads to a “JT-liquid” with local tetragonal distortions and yet macroscopic cubic symmetry. At intermediate doping (x ≃ 0.25) a transition from a large-distortion polaronic insulator to a small-distortion metal with correlated electrons takes place, as observed in the ferromagnetic phase in the manganites.