Quasi-particle excitations in a ferromagnet, near a quantum critical point

Abstract

The quasi-particle excitations of a ferromagnet, near a quantum critical point are examined. The weak ferromagnetic state is described by the Hubbard model. The effects of emission of absorption of Goldstone modes on the quasi-particles is examined, as are the effects of the incoherent spin–flip excitations. It is found that, unlike the strong ferromagnet, the Goldstone modes have negligibly small effects on the quasi-particle spectrum and the strongest effects originate from the incoherent spin–flips. The incoherent spin excitations produce large quasi-particle mass enhancements and also produce an incoherent peak in both the off Fermi energy majority and minority spin spectral density.