Dynamic structure factor for 3He in two dimensions

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 [H. Godfrin et al., Nature 483, 576 (2012)]. Here we address the study of 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, this scheme affords an extremely convincing description of the experimental findings.