d-wave, dimer, and chiral states in the two-dimensional Hubbard model

The ground-state properties of two holes on a 4×{}4 Hubbard cluster have been studied using a Lanczos algorithm at intermediate coupling U=4. Several states have been found to lie within a very small energy range at the bottom of the spectrum. Although many properties of these states are remarkably similar, their overall symmetries are quite different, suggesting different possible scenarios in larger systems.