Nearest-neighbor attraction stabilizes staggered currents in the two-dimensional Hubbard model

Using a strong-coupling approach, we show that staggered current vorticity does not obtain in the repulsive two-dimensional Hubbard model for large on-site Coulomb interactions, as in the case of the copper oxide superconductors. This trend also persists even when nearest-neighbor repulsions are present. However, staggered flux ordering emerges when attractive nearest-neighbor Coulomb interactions are included. Such ordering opens a gap along the (π,O)-(O,π) direction and persists over a reasonable range of doping.