Using quasimonochromatic relaxation phonons emitted by superconducting tunneling functions, the phonon transfer through real solid-liquid helium interfaces was tested. We found an enhancement of the energy transmission if the incident phonons exceed the threshold energy Eo = 0.32 meV. This sharp threshold energy shifts to 0.42 meV if the lighter isotope 3 He is used.
(1983) Koblinger, Otto; Heim, Ulrich; Welte, Michael; Eisenmenger, Wolfgang
Phonons emitted by superconducting tunneling junctions into insulator crystal substrates exhibit a sharp amplitude reduction above 85 GHz if the tunneling diodes are covered by 4He. This is attributed to the onset of an enhanced phonon transport into helium.
