Stripes and Spin Incommensurabilities Are Favored by Lattice Anisotropies

Structural distortions in cuprate materials give a natural origin for anisotropies in electron properties. We study a modified one-band $t-J$ model in which we allow for different hoppings and antiferromagnetic couplings in the two spatial directions ( $t_x\ne t_y$ and $J_x\ne J_y$). Incommensurate peaks in the spin structure factor show up only in the presence of a lattice anisotropy, whereas charge correlations, indicating enhanced fluctuations at incommensurate wave vectors, are present but almost unaffected with respect to the isotropic case.