Electron Correlation and Jahn-Teller Interaction in Manganese Oxides

TL;DR

This paper investigates how electron-electron repulsion and Jahn-Teller electron-phonon interactions influence the electronic properties of manganese oxides, revealing their combined effects on bandwidth reduction and phonon spectrum features.

Contribution

It provides a detailed theoretical analysis of the interplay between Coulomb and Jahn-Teller interactions in manganese oxides, highlighting the significance of phonon retardation effects.

Findings

Jahn-Teller and Coulomb interactions induce local orbital moments.

Retardation effects of phonons significantly reduce bandwidth.

Phonon spectrum features a temperature-independent peak and a Kondo peak.

Abstract

The interplay between the electron repulsion $U$ and the Jahn-Teller electron-phonon interation $E_{LR}$ is studied with a large $d$ model for the ferromagnetic state of the manganese oxides. These two interactions collaborate to induce the local isospin (orbital) moments and reduce the bandwidth $B$. Especially the retardation effect of the Jahn-Teller phonon with the frequency $\Omega$ is effective to reduce $B$, but the strong $\Omega$-dependence occurs even when the Coulombic interaction is dominating ($ U >> E_{LR}$) as long as $E_{LR} > \Omega$. The phonon spectrum consists of two components, i.e., the temperature independent sharp peak at $\omega = {\tilde \Omega} = \Omega [(U +4 E_{LR})/U]^{1/2}$ and that corresponding to the Kondo peak. These results compared with the experiments suggest that $\Omega <E_{LR} <U$ in the metallic manganese oxides.