Spiral ferrimagnetic phases in the two-dimensional Hubbard model

We address the possibility of spiral ferrimagnetic phases in the mean-field phase diagram of the two-dimensional (2D) Hubbard model. For intermediate values of the interaction U ( 6 ≲ U / t ≲ 11 ) and doping n, a spiral ferrimagnetic phase is the most stable phase in the (n,U) phase diagram. Higher values of U lead to a non-spiral ferrimagnetic phase. If phase separation is allowed and the chemical potential μ replaces the doping n as the independent variable, the ( μ , U ) phase diagram displays, in a considerable region, a spiral (for 6 ≲ U / t ≲ 11 ) and non-spiral (for higher values of U) ferrimagnetic phase with fixed particle density, n=0.5, reflecting the opening of an energy gap in the mean-field quasi-particle bands