Pressure dependence of elementary excitations in normal liquid 3He

Abstract

The density and spin–density excitations in normal liquid 3He under applied pressure are described within a simple RPA model employing the Landau quasiparticle–quasihole interaction. Damping of the zero-sound mode to multi-quasiparticle–hole pairs is also included. The zero-sound mode energy is predicted to increase markedly with pressure while the quasiparticle–hole spectrum energy decreases with pressure. The paramagnon mode remains largely unchanged. Damping of zero sound also increases with pressure. This increase coupled with a decrease in coherent neutron scattering intensity from liquid 3He suggests the zero-sound mode will be more difficult to observe at elevated pressures than at zero pressure. In the present model the pressure dependence of the excitations follows directly from the pressure dependence of the Landau quasiparticle–quasihole interaction.