Charge-Orbital Stripe Structure inLa1−xCaxMnO3(x=1/2,2/3)

Abstract

We propose the origin of the charge-ordered stripe structure with the orbital ordering observed experimentally in ${\mathrm{La}}_{1-x}{\mathrm{Ca}}_x{\mathrm{MnO}}_3$ ( $x=1\mathrm{}/2,2/3$), 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 interaction ( $V$) with the Hartree-Fock approximation. Both the charge and orbital ordering structures observed in experiments are reproduced for a wide region of the $U-V$ phase diagram. The stability of the orbital ordering is also confirmed by perturbation theory.