Ordered states in the disordered Hubbard model

The Hubbard model is studied in which disorder is introduced by putting the on-site interaction to zero on a fraction f of (impurity) sites of a square lattice. Using quantum Monte Carlo methods and dynamical mean-field theory we find that antiferromagnetic long-range order is initially enhanced at half-filling and stabilized off half-filling by the disorder. The Mott–Hubbard charge gap of the pure system is broken up into two pieces by the disorder: one incompressible state remains at average density n=1 and another can be seen slightly below n=1+f. Qualitative explanations are provided.