Effective mass, spin fluctuations, and zero sound in liquid He-3

We have measured and calculated the density and spin-density dynamic struct ure factors S-c(Q,omega) and S-I(Q,omega) of normal liquid He-3 as a functi on of wave vector Q and temperature T. The static spin susceptibility chi(T ) and specific heat C-V(T) are also calculated. These properties all depend upon the effective mass m*(k,omega) of the Fermi quasiparticles making up the liquid. We use a model in which m* peaks near the Fermi surface to m* = 2.8, the Landau theory effective mass, and decreases toward the bare mass m* = 1 for quasi particles away from the Fermi energy epsilon(F). The theor y for all the properties may be viewed as Landau theory with an effective m ass m*(epsilon(k))=m*(k) that decreases as the quasiparticle energy epsilon (k) moves away from epsilon(F). The peaking of m* at epsilon(F) is widely p redicted in Fermi systems and the aim is to test how important this physica l feature is in the dynamics of liquid He-3. We find that S-c(Q,omega) and S-I(Q,omega) versus Q and T as well as chi(T) are well reproduced by the mo del for the same m*(k). The CV(T) can be reproduced, but a much lower value of m*(k) at energies epsilon(k) away from epsilon(F) is required, m*=0.5, as found in previous calculations of C-V(T). We conclude that the peaking o f m* at epsilon(F) is an important physical feature to include in calculati ons of S(Q,omega) and that the quasiparticle model itself is inadequate for C-V at higher temperatures.