Strong phonon conversion at the helium-solid interface

Abstract

Tunable monochromatic phonon pulses (130 to 870 GHz) were scattered at solid surfaces covered with various amounts of helium. A strong phonon loss due to only 3 atomic layers was observed which was independent of frequency and did not exhibit structure due to the helium dispersion. The results indicate strong frequency conversion at the interface, and thus suggest a new approach to the Kapitza-resistance problem. © 1974 The American Physical Society.