Ferromagnetism in the Hubbard model and Hund's rule

摘要: Abstract We investigate the Hubbard model with a Nd-fold degenerate single particle ground state. If number of electrons satisfies Ne⩽Nd, has ferromagnetic multiparticle states. give necessary and sufficient condition for state to be unique if Ne=Nd. It is spin S= 1 2 N e . As corollary, we obtain Hund's rule general eigenstates on translationally invariant lattices in special case, where each states filled one electron.