EMP is funded through the Horizon2020 programme of the European Commission.
Selected Publications

Transport and Phonon Damping in 4He

K. Beauvois, H. Godfrin, E. Krotscheck, R. E. Zillich

The dynamic structure function S(k,ω) informs about the dispersion and damping of excitations. We have recently (Beauvois et al. in Phys Rev B 97:184520, 2018) compared experimental results for S(k,ω) from high-precision neutron scattering experiments and theoretical results using the “dynamic many-body theory” (DMBT), showing excellent agreement over the whole experimentally accessible pressure regime. This paper focuses on the specific aspect of the propagation of low-energy phonons. We report calculations of the phonon mean-free path and phonon lifetime in liquid 4 He as a function of wavelength and pressure. Historically, the question was of interest for experiments of quantum evaporation. More recently, there is interest in the potential use of 4 He as a detector for low-energy dark matter (Schulz and Zurek in Phys Rev Lett 117:121302/1, 2016). While the mean-free path of long wavelength phonons is large, phonons of intermediate energy can have a short mean-free path of the order of μm . Comparison of different levels of theory indicates that reliable predictions of the phonon mean-free path can be made only by using the most advanced many-body method available, namely DMBT.

J. Low Temp. Phys. 197, 113 (2019)

doi: 10.1007/s10909-019-02219-1