Charge stripes in the extended Hubbard model with nearest-neighbor Coulomb interaction

Using a strong coupling approach, based on a Cumulant Expansion, we investigate the stripe orders driven by nearest-neighbor Coulomb (NNC) interaction in the Hubbard model. When we consider only local Coulomb repulsion, critical charge fluctuations drive the system towards a phase separation (PS). Such density instability evolves into an incommensurate charge density wave (ICDW) when nonlocal Coulomb interactions are taken into account, similarly to the case when long-range Coulomb forces are considered. In particular, we find a stripe phase with a crossover from diagonal to vertical stripes in the doping region 0.03 ?x? 0.2, similarly to neutron scattering experiments on La2 - xSrxCuO4. Analogous strong dependence in the stripe direction is observed at varying the NNC interaction.