A New Kapitza Investigation: Detecting Backscattered Phonons with Tunnel Junction and Bolometer Simultaneously

Abstract

At phonon frequencies above c.100 GHz the heat transfer across the interface between a solid and helium increases drastically over the values expected by the acoustical mismatch of the two materials. ¹ In the acoustical model it is assumed that phonons are transmitted directly i.e. without changing their frequencies. In this paper, however, we will show that the phonons undergo frequency conversion in the first two atomic layers of helium at the solid.