Abstract
We study a class of Hubbard models in which the corresponding single-electron ground states have bulk degeneracy. We prove that the ground states of the models exhibit ferromagnetism when the electron filling factor is not more than and sufficiently close to =‖V‖/2‖Λ‖ (where ‖V‖ is the dimension of degeneracy and ‖Λ‖ is the number of sites), and exhibit paramagnetism when the filling factor is sufficiently small. This is the first time that a three-dimensional itinerant-electron system is proved to exhibit ferromagnetism in a finite range of the electron filling factor.
- Received 19 May 1992
DOI:https://doi.org/10.1103/PhysRevLett.69.1608
©1992 American Physical Society