Publikationsrepositorium - Helmholtz-Zentrum Dresden-Rossendorf

Due to its nature as a strongly correlated quantum liquid, ultracold helium is characterized by the nontrivial interplay of different physical effects. Bosonic 4He exhibits superfluidity and Bose-Einstein condensation. Its physical properties have been accurately determined on the basis of ab initio path integral Monte Carlo (PIMC) simulations. In contrast, the corresponding theoretical description of fermionic 3He is severely hampered by the notorious fermion sign problem, and previous PIMC results have been derived by introducing the uncontrolled fixed-node approximation. In this work, we present extensive new PIMC simulations of normal liquid 3He without any nodal constraints. This allows us to to unambiguously quantify the impact of Fermi statistics and to study the effects of temperature on different physical properties like the static structure factor S(q) , the momentum distribution n(q) , and the static density response function χ(q). In addition, the dynamic structure factor S(q, ω) is rigorously reconstructed from imaginary-time PIMC data. From simulations of 3He , we derived the familiar phonon–maxon–roton dispersion function that is well-known for 4He and has been reported previously for two-dimensional 3He films (Nature 483:576–579 (2012)). The comparison of our new results for both S(q) and S(q, ω) with neutron scattering measurements reveals an excellent agreement between theory and experiment.