Second sound waves in diamond

The possibility of propagation of second sound waves in diamond single crystals depending on their dimensions, concentrations of isotopes and temperature is studied. At this correct account of phonon scattering on boundaries is important. The calculation of phonon collision frequencies is carried out in the reduced isotropic crystal model using second and third modules of elasticity and in Callaway model on the basis of experimental data on diamond thermal conductivity. Both models give us the consistent values of parameters under which the propagation of SSW is possible. It is discovered in concentrations of isotopes 13C < 10− 6, temperatures T < 80 K. Such a good agreement provides the reliability of received results and shows the efficiency of reduced isotropic crystal model in the description of diamond properties in low temperature range.

► Calculations of SSW dumping coefficient in diamond are carried out in the reduced isotropic crystal model and Callaway model.
► The region of SSW existence as function of temperature, sample dimensions and isotopeconcentrations is found.
► A detailed analysis of the results is carried.
► Critical values of the parameters of SSW existence in diamond are found.