SIMPLE THEORETICAL-ANALYSIS OF THE LOW-ENERGY SPIN FLUCTUATION PEAK OBSERVED BY NEUTRONS IN LIQUID-HE-3

We present a simple analysis of the low-energy spin fluctuation peak recently observed at Argonne in neutron experiments performed on liquid 3He at low temperature. From the energy position of the peak, we extract values for the spin-spin interaction (supposed to be of contact type) and the effective mass which agree amazingly well with those used in the paramagnon picture, which assumes liquid 3He to be close to ferromagnetic. This allows a theoretical curve for the incoherent part of the neutron inelastic scattering function to be drawn without any adjustable parameter: the only one that has been extracted from the neutron data. Then, by subtraction from the experimental total scattering function, we obtain an approximate shape for the coherent part containing the zero-sound mode also observed in these experiments. More data, in particular for smaller momentum transfer would be most useful for confirming the above result, and also possibly for building up a one-parameter model for the zero-sound mode, analogous to the one-parameter model (paramagnon) for the spin fluctuation pseudo mode. © 1979 Plenum Publishing Corporation.