Transport and Phonon Damping in $^{\bf 4}$He
Abstract
The dynamic structure function informs about the dispersion and damping of excitations. We have recently (Phys. Rev. B {\bf 97}, 184520 (2018)) compared experimental results for from high-precision neutron scattering experiment 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 life time in liquid \he4 as a function of wave length and pressure. Historically, the question was of interest for experiments of quantum evaporation. More recently, there is interest in the potential use of He as a detector for low-energy dark matter (K. Schulz and Kathryn M. Zurek, Phys. Rev. Lett. {\bf 117}, 121302 (2016)). While the mean free path of long wave length phonons is large, phonons of intermediate energy can have a short mean free path of the order of m. Comparison of different levels of theory indicate that reliable predictions of the phonon mean free path can be made only by using the most advanced many--body method available, namely, DMBT.
Keywords
Cite
@article{arxiv.1905.04759,
title = {Transport and Phonon Damping in $^{\bf 4}$He},
author = {K. Beauvois and H. Godfrin and E. Krotscheck and R. E. Zillic},
journal= {arXiv preprint arXiv:1905.04759},
year = {2019}
}