Double Degeneracy and Jahn-Teller Effects in CMR Perovskites

TL;DR

This paper investigates Jahn-Teller effects and electron correlations in CMR perovskites, revealing how static distortions and fluctuations influence charge transport and carrier character.

Contribution

It introduces a combined approach using Gutzwiller and Lang-Firsov approximations to study JT effects and electron correlations in manganites.

Findings

Charge carrier character depends on static JT distortion.

JT fluctuations contribute to charge transport.

Two-component JT coupling influences electron dynamics.

Abstract

Jahn-Teller (JT) electron-phonon coupling effects in the colossal magnetoresistance perovskite compounds $La_{1-x}A_xMnO_3$ are investigated. Electron-electron correlations between two degenerate Mn $e_g$ orbitals are studied in the Gutzwiller approximation. The static JT distortion and antiadiabatic polaron effects are studied in a modified Lang-Firsov approximation. We find that (i) the electron or hole character of the charge carrier depends on the static JT distortion, and (ii) due to the two-component nature of the JT coupling, fluctuations in the JT distortion direction contribute to the charge transport in similar fashion as the local spins.