On the description of nearly ferromagnetic fermion systems

H. Stern, R. Brout

Harald Grosse, Victor Nikolaevich Popov

Jeffrey B. Sokoloff

Nagoaka's result that the ground state of the near-neighbor-hopping Hubbard model, for a nearly half-filled band and for interaction strength much greater than hopping energy, is ferromagnetic, is shown to be valid for bosons with spin, as well as fermions, in a finite system. In the thermodynamic limit, the boson system is shown to be nonmagnetic. Ferromagnetism is argued to exist at nonzero temperatures for fermions in an infinite system, and upper and approximate lower bounds are obtained for the Curie temperature.

Andrey V. Chubukov

We analyze the behavior of interacting fermions near a ferromagnetic Stoner instability. We show that the Landau damping of the spin susceptibility is a relevant perturbation near a ferromagnetic quantum-critical point (FQCP). We argue that, as the system approaches FQCP, the fermionic self-energy crosses over from predominantly momentum dependent away from the transition to predominantly frequency dependent in the immediate vicinity of the transition. We argue that due to this self-generated locality, the quasiparticle effective mass does not diverge before FQCP.

Bent E. Sørensen

Bent Sørensen