Second sound waves in diamond

TL;DR

This paper investigates the conditions under which second sound waves can propagate in diamond single crystals, considering factors like isotope concentration, temperature, and crystal dimensions, using phonon scattering models.

Contribution

It introduces a combined approach using reduced isotropic crystal and Callaway models to accurately predict second sound wave propagation in diamond at low temperatures.

Findings

Second sound propagation is possible in diamonds with isotope concentration < 10^-5.

Propagation occurs at temperatures below 90K.

Models show consistent parameters confirming the feasibility of second sound in diamond.

Abstract

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 that concentrations of isotopes 13C < 10-5, temperatures T < 90K. 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.