Origin of the Charge-Orbital Stripe Structure in La_(1-x)Ca_(x)MnO_(3) (x=1/2, 2/3)

TL;DR

This paper investigates the origin of charge and orbital stripe structures in La_(1-x)Ca_(x)MnO_(3) using a Hubbard model with Coulomb interactions, revealing the essential role of long-range Coulomb forces in stabilizing observed orderings.

Contribution

It demonstrates that the long-range Coulomb interaction is crucial for the formation of charge-orbital stripe structures in La_(1-x)Ca_(x)MnO_(3), using a Hubbard model and Hartree-Fock approximation.

Findings

Reproduces experimental charge and orbital orderings in a phase diagram.

Confirms orbital ordering stability through perturbation theory.

Highlights the importance of long-range Coulomb interactions.

Abstract

We propose the origin of the charge-ordered stripe structure with the orbital ordering observed experimentally in La_(1-x)Ca_(x)MnO_(3) (x=1/2, 2/3), in which the long-range Coulomb interaction plays an essential role. We study a Hubbard model with doubly-degenerate e_g orbitals, and treat the on-site Coulomb interaction (U) and the nearest-neighbor one (V) with the Hartree-Fock approximation. Both the charge and orbital ordering structures observed in experiments are reproduced in a wide region of the U-V phase diagram determined by the present study. The stability of the orbital ordering is also confirmed by the perturbation theory.