The influence of normal-to-superconductive transition on phonon transmission through liquid 4He - metal interface
Zinov'eva K.N., Narmoneva D.A., Semenov A.S.
The passage of low frequency phonons through the liquid 4He aluminum single crystal interface has been studied The measurements were carried out at temperatures 100 300 mK and frequencies 13-91 MHz for both normal and superconductive states of aluminum. It is demonstrated that Rayleigh wave contribution into total energy flux across the boundary drop3 drastically in going from normal to superconductive state of metal. Experimental data are compared with those on copper reported before and the conclusion is made that the scattering of surface wave (similarly to the bulk waves) is due to conduction electrons. The bulk interference of phonons (analogous to Fabri-Perot interference) is also observed for superconductive metal, while for normal state this effect is missing.