Charge Orderings and Phase Separations in the Atomic Limit of the Extended Hubbard Model with Intersite Density-Density Interactions |

K. Kapcia, W. Kłobus and S. Robaszkiewicz
Electron States of Solids Division, Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań, Poland |

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A simple effective model of charge ordered insulators is studied. The tight binding Hamiltonian consists of the effective on-site interaction U and the intersite density-density interactions W_{ij} (both: nearest-neighbour and next-nearest neighbour). In the analysis of the phase diagrams we have adopted the variational approach, which treats the on-site interaction term exactly and the intersite interactions within the mean-field approximation. The phase separated states have not been taken into account in previous analyses. Our investigations of two cases of the on-site interaction: attraction (U/(- W_{Q}) = - 10) and repulsion (U/(- W_{Q}) = 1.1) show that, depending on the values of the next-nearest neighbour attraction, the system can exhibit not only homogeneous phases: charge ordered and nonordered, but also various phase separated states (charge ordered-nonordered, charge ordered-charge ordered). |

DOI: 10.12693/APhysPolA.118.350 PACS numbers: 71.10.Fd, 71.45.Lr, 64.75.Gh, 71.10.Hf |