Stripe orders driven by long-range Coulomb forces in the 2D-Hubbard model

Within the single band 2D-Hubbard model treated by means of a strong-coupling approach based on a cumulant expansion and a nonstandard diagrammatic technique, we discuss the existence of critical charge fluctuations that could give rise to an instability towards a phase separation (PS). It turns out that such instability exists and evolves into an incommensurate charge density wave (ICDW) when long-range Coulomb forces are taken into account. We find a stripe phase with a crossover from diagonal to vertical stripes at increasing doping in the range 0.01 ?δ? 0.2 and increasing Coulomb potential U, similarly to recent NMR experiments on La _{2 - x} Sr _x CuO ₄. Received 20 November 2000