Correlations and Coherence at Different Scales (CCDS25)

Despite being well known for its strong anti-ferromagnetic correlations, under the right conditions, the Fermi-Hubbard model can also host ferromagnetism. Here, we explore two phenomena that drive the system on different geometries to ferromagnetic states, the Nagaoka effect at extreme interaction strengths on the triangular and square lattices, and the flat band physics on the Kagome lattice. We study short-range spin correlations and other thermodynamic properties at finite temperatures using numerically exact methods and identify the regions with dominant ferromagnetic correlations in each case. We also discuss the relevance of our results to recent observations with ultracold atoms in optical lattices.