Charge-orbital stripe structure in La1-xCaxMnO3 (x=1/2, 2/3)

We propose the origin of the charge-ordered stripe structure with the orbital ordering observed experimentally in La1-xCaxMnO3 (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 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.