An observation of second sound in sapphire
Danil'chenko B.A. , Poroshin V.N. , Sarbei O.G.
The propagation of acoustic oscillation modes in sapphire was investigated by using the method of heat pulses. In addition to ballistic phonon propagation, the propagation of heat in the form of "second sound" was observed for the first time. The relaxation times of the resistive and normal phonon scattering processes are estimated.
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![](/ps/1364/article_20620_800_head.png "The propagation of acoustic oscillation modes in sapphire was investigated by using the method of heat pulses. In addition to ballistic phonon propagation, the propagation of heat in the form of "second sound" was observed for the first time. The relaxation times of the resistive and normal phonon scattering processes are estimated.")