Coupling of the zero sound to transverse spin waves for neutral and normal Fermi liquids in dc magnetic field at precessing magnetization

Abstract

Following the idea by Ketterson, this author showed that in neutral and normal Fermi liquids, the polarization effects lead to coupling of transverse spin waves to zero sound at precessing magnetization of the system. The observable effects, at the range of dc fields applied to3He, can appear only if the zero sound is degenerate with transverse spin waves excited in the reference frame rotating with the Larmor frequency about theH dc-axis. This possibility is investigated at Landau parameters vanishing atl>1 and nonzero, though small, coupling of the density to the spin density and the particle current to the spin current, resulting from the polarization of the system byH dc. The degeneration is, in general, possible but, at large values of the zero sound velocity with respect to the Fermi velocity, caused by large values of the Landau parameterF 0 and alsoF 1 for3He, atF 0 ≲−0.7, it appears only at positiveF 1 . All experimental estimations of this parameter agree in its negativity excluding the degeneration of the zero sound and transverse spin waves for3He.