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(U_i) = (1-f)delta(U_i-U) + fdelta(U_i), is studied using a finite temperature quantum Monte Carlo technique and dynamical mean-field theory. We find 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.