Valence-bond approach to two-dimensional broken symmetries: Application toLa2CuO4

We use a real-space approach to geometric broken symmetries to show that the on-site electron correlation destroys the bond alternation in a square lattice, even though this interaction enhances the one-dimensional bond alternation. Boundary lines between charge- and spin-density waves are derived for nonzero short-range intersite Coulomb correlations. Implications for systems like ${\mathrm{La}}_2$Cu${\mathrm{O}}_4$ are briefly discussed.