Indications of a metallic antiferromagnetic phase in the two-dimensional U-t-t|IHmodel

We present mean-field and quantum Monte Carlo results that suggest the existence of an itinerant antiferromagnetic ground state in the half-filled U-t-${\mathrm{t}}^{|\mathrm{I}\mathrm{H}}$ model in two dimensions. In particular, working at ${\mathrm{t}}^{|\mathrm{I}\mathrm{H}}$/t=-0.2 we found that antiferromagnetic long-range order develops at ${\mathrm{U}}_{\mathrm{c}1\mathrm{}}$/t≈2.5±0.5, while a study of the density of states N(ω) and the response to an external magnetic field indicates that the system becomes insulating at a larger coupling 4<${\mathrm{U}}_{\mathrm{c}2\mathrm{}}$/t<6.