Zero-sound mode in a neutral Fermi liquid : dynamic fermionic correlations applied to 2D 3He

Recent neutron scattering experiments on 3He films have observed a zero-sound mode [H. Godfrin, et al., Nature 483, 576 (2012)], its dispersion relation and its merging with -and possibly emerging from- the particle-hole continuum. Here we address the study of the excitations in the system via quantum Monte Carlo methods: we suggest a practical scheme to calculate imaginary time correlation functions for moderate-size fermionic systems. Combined with an efficient method for analytic continuation [E. Vitali, M. Rossi, L. Reatto, D.E. Galli, Phys. Rev. B 82, 174510 (2010)], this scheme affords an extremely convincing description of the experimental findings.