Enhancement of long-range antiferromagnetic order by nonmagnetic impurities in the Hubbard model

The two-dimensional Hubbard model with a bimodal distribution of on-site interactions, P(Ui) = (1 − f)δ(Ui − U) + fδ(Ui), is studied using finite-temperature Quantum Monte Carlo and dynamical mean-field theory. Long-range antiferromagnetic order off half-filling is stabilized by the disorder, due to localization of the dopants on the U = 0 sites. Whereas in the clean model there is a single gap at n = 1, for nonzero f we find the compressibility and density of states exhibit gaps at two separate fillings.