The dynamics of superfluid 4He

TL;DR

This paper investigates the dynamic response of superfluid helium-4 using neutron scattering and a perturbation theory approach, highlighting the dominant role of Bose statistics over the condensate in shaping observed behaviors.

Contribution

It provides a simple density fluctuation model that explains superfluid helium-4's dynamic features and their temperature dependence, emphasizing the minor role of the Bose condensate.

Findings

Dynamic response features are mainly due to Bose statistics.

Temperature variations significantly affect the response.

Bose condensate has a minor impact on dynamics.

Abstract

We present neutron scattering results for the dynamic response by superfluid and normal-fluid 4He and the results of a simple perturbation-theory analysis which allows us to describe all aspects of the observed behavior by considering only density fluctuations. We show that the three key features that are characteristic of the dynamic reponse of superfluid 4He, as well as their dramatic variations with temperature, can be attributed predominantly to the Bose statistics obeyed by all the 4He atoms. It appears that the presence of the Bose condensate exerts at most a minor influence on the dynamic response.