INTERACTION OF SOFT MODES AND SOUND-WAVES IN GLASSES

The interaction of sound waves with tunneling, relaxational, and resonant vibrational states in glasses is investigated within the soft-potential model. The same bilinear coupling constant is assumed for all three different kinds of soft modes. The model reproduces the results of the tunneling model at low temperatures and frequencies. In addition, it explains the fast rise of the relaxational absorption above 1 K and the plateau in the thermal conductivity around 5 K. The universal features of the sound absorption in glasses are described with good accuracy up to 20 K.