The Effect of Randomness on Long-Range Order in the Two-Dimensional Half-Filled Hubbard Model

Quantum Monte Carlo simulations are used to determine the effects of disorder on magnetic, charge density wave, and superconducting correlations in the two-dimensional half-filled Hubbard model. In the repulsive case, random site energies and random intersite hybridizations destroy long range antiferromagnetic order by interfering with moment formation and by the creation of independent singlet bonds, respectively. In the attractive model, random site energies break the symmetry between charge density and pairing fluctuations in favor of the superconducting phase. Finally, we suggest a bimodal distribution of repulsive on-site interactions might allow the separation of magnetic and Mott transitions.