An effective Hamiltonian for an extended Kondo lattice model and a possible origin of charge ordering in half-doped manganites

TL;DR

This paper derives an effective Hamiltonian for a strongly interacting extended Kondo lattice model, proposing a charge ordering mechanism in half-doped manganites driven by electron hopping processes leading to a Wigner lattice formation.

Contribution

It introduces a new effective Hamiltonian for the model and suggests a physical mechanism for charge ordering in manganites based on virtual electron hopping processes.

Findings

Charge ordering may be driven by electron hopping leading to a Wigner lattice.

Spins of electrons are ferromagnetically aligned in the Wigner lattice phase.

The phase diagram of the ground state at half doping is presented.

Abstract

An effective Hamiltonian is derived in the case of the strong Hund coupling and on-site Coulomb interaction by means of a projective perturbation approach. A physical mechanism for charge ordering in half-doped manganites (R_{0.5}X_{0.5}MnO_3) is proposed. The virtual process of electron hopping results in antiferromagnetic superexchange and a repulsive interaction, which may drive electrons to form a Wigner lattice. The phase diagram of the ground state of the model is presented at half doping. In the case of formation of Wigner lattice, we prove that spins of electrons are aligned ferromagnetically as well as that the localized spin background is antiferromagnetic. The influence of the on-site Coulomb interaction is also discussed.