Zero-sound mode in a neutral Fermi liquid: dynamic fermionic correlations applied to two-dimensional 3He

Recent neutron scattering experiments on 3He films have observed a zero-sound mode, its dispersion relation and its merging with - and possibly emerging from - the particle-hole continuum. We develop a practical quantum Monte Carlo scheme to calculate imaginary time correlation functions for moderate-size fermionic systems. Combined with an efficient method for analytic continuation, this scheme affords an extremely convincing description of the experimental findings.