Doping Dependence of Kinetic Ferromagnetism in the Square Lattice Hubbard Model

Itinerant electron models can host a ferromagnetic phase in the limit of extreme interactions at non-commensurate fillings. In our work, we explore this kinetic ferromagnetism within the square lattice Fermi-Hubbard model, and its strong-coupling counterpart, the t−J model, via the numerical linked-cluster expansions. We find evidence of ferromagnetic Nagaoka polarons at finite temperatures at dopings up to ∼33% away from half filling. We map out the boundaries of this phase based on various two-point and three-point correlation functions.