Zero Temperature Insulator-Metal Transition in Doped Manganites

TL;DR

This paper models the zero-temperature insulator-metal transition in doped manganites, incorporating Jahn-Teller phonons and Coulomb interactions, and finds a phase diagram consistent with experimental observations.

Contribution

It introduces a comprehensive low-energy model capturing Jahn-Teller effects, electron correlations, and phase coexistence in manganites, explaining their transition behavior.

Findings

Phase diagram aligns with experiments for realistic parameters.

Coexistence of localized and band-like electronic states.

Transition depends on doping, Coulomb strength, and Jahn-Teller energy.

Abstract

We study the transition at T=0 from a ferromagnetic insulating to a ferromagnetic metallic phase in manganites as a function of hole doping using an effective low-energy model Hamiltonian proposed by us recently. The model incorporates the quantum nature of the dynamic Jahn-Teller(JT) phonons strongly coupled to orbitally degenerate electrons as well as strong Coulomb correlation effects and leads naturally to the coexistence of localized (JT polaronic) and band-like electronic states. We study the insulator-metal transition as a function of doping as well as of the correlation strength U and JT gain in energy E_{JT}, and find, for realistic values of parameters, a ground state phase diagram in agreement with experiments. We also discuss how several other features of manganites as well as differences in behaviour among manganites can be understood in terms of our model.