They are characterized by an electron-electron interaction much larger than the hopping term.
In reference to these materials, the extended Brinkman-Rice picture was introduced. A Bose-Einstein condensate in a 3D  optical lattice undergoes a transition from superfluid to this state as the potential depth of the lattice is increased. One  subtype of these materials is a result of a thermodynamic phase transition in which the pre-formed local magnetic  moments antiferromagnetically order. One model that successfully explains their existence includes a kinetic energy term  and a namesake U parameter. The (*) Hubbard model describes these materials, which constitute the second category of a set of materials whose first category includes band, Peierls, and Anderson types, making them a result of a cooperative many-electron  phenomenon. They are characterized by an electron-electron interaction much larger than the hopping term. For 10 points, name  these materials that are predicted, by band theory, to be conductors, but are actually insulators.
In reference to these materials, the extended Brinkman-Rice picture was introduced.
Mott insulators [accept just Mott after “insulators”; prompt on Mott or insulators or Mott transition metal-insulator transition at any point]