Orbital superlattice in the degenerate Hubbard model

M. Cyrot , C. Lyon-Caen

We study some effects of the orbital degeneracy in narrow band solids using a doubly degenerate Hubbard model. When there is exactly one electron per atom the ground state is ferromagnetic and an orbital superlattice is set up : the lattice breaks up into two sublattices, each with predominantly one of the orbital states. We discuss the importance of the intraatomic exchange energy for the stability of this state. We calculate the collective excitations corresponding to this ground state in the RPA : we find, besides the spin wave modes, a new kind of excitation linked with the orbital superlattice : the orbital waves. The effect of temperature is investigated in the molecular field approximation : the orbital superlattice disappears at a higher temperature than the Curie temperature.

Mots clés: band model of magnetism; ferromagnetism; spin waves

Domaines: Articles anciens

M. Cyrot, C. Lyon-Caen. Orbital superlattice in the degenerate Hubbard model. Journal de Physique, 1975, 36 (3), pp.253-266. ⟨10.1051/jphys:01975003603025300⟩. ⟨jpa-00208250⟩