@article{oai:niigata-u.repo.nii.ac.jp:00002555, author = {Takeno, Shozo and Goda, Masaki}, issue = {3}, journal = {Progress of theoretical physics, Progress of theoretical physics}, month = {Sep}, note = {An attempt is made to formulate a theory of phonon-like excitations in liquid helium by generalizing the theory of phonons in quantum crystals to quantum disordered systems. By using experimental data for pair correlation functions, dispersion curves of longitudinal phonon modes are calculated, with a result for their over-all behavior in fairly good agreement with phonon-roton dispersion curves obtained by neutron scattering measurements. It is shown that the temperature-dependence of the calculated roton-minimum is in good agreement with experiment for liquid helium I, but not for liquid helium II. A brief discussion is given on the nature of rotons in liquid helium. It is suggested that, within certain restrictions, the roton spectrum in liquid helium is likely to be a general feature of the dispersion of elementary excitations in liquids, classical or quantum.}, pages = {724--730}, title = {Phonon-Like Excitations in Liquid Helium}, volume = {48}, year = {1972} }