Spin‐charge fluctuations in itinerant helical magnets

Abstract

Abstract. Using a generalized random phase approach quantum fluctuations beyond the helical mean-field states of the Hubbard model off half filling are discussed. The collective mode spectrum is shown to exhibit spin-charge mixing and is found to be strongly renormalized by coupling to low-energy incoherent particle-hole excitations. Results for the collective mode dispersion whlch displays a significant anisotropy are presented for selected helical phases. Moreover phase space regions of 'missing' modes are identified with a finite wave length instability of the helical states suggesting novel inhomogeneous phases of the doped Hubbard model. P.A.C

Weak-coupling Mean-field Theory of Magnetic Properties of NiGa2S4

“…Furthermore, the spin excitation modes are generally coupled with charge modes in incommensurate spiral ordering states even for much larger U. 30,31) This coupling is completely neglected in localized spin approaches, where there are no degrees of freedom in the charge sector.…”