Hubbard models with nearly flat bands: Ground-state ferromagnetism driven by kinetic energy
Hubbard models with nearly flat bands: Ground-state ferromagnetism driven by kinetic energy
We consider the standard repulsive Hubbard model with a flat lowest-energy band for two one-dimensional lattices (diamond chain and ladder) as well as for a two-dimensional lattice (bilayer) at half filling of the flat band. The considered models do not fall in the class of Mielke-Tasaki flat-band ferromagnets, since they …