Second-Sound Propagation in Dielectric Solids

Abstract

The conditions necessary for the occurrence of second sound in solids are examined in some generality. The results indicate that second sound can propagate at frequencies greater than the reciprocal umklapp relaxation time and smaller than the reciprocal normal relaxation time. At frequencies less than the reciprocal umklapp relaxation time, the solutions are the same as those for normal thermal conductivity. The frequency range and damping of second sound at various temperatures is computed using relaxation times determined for sodium fluoride.