Acoustoelectric Waves in Piezoelectric Materials

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Abstract
The electron‐piezoelectric sound wave interaction gives rise to three distinguishable phenomena: gain, acoustoelectric effects, and nonlinear mixing. The acoustoelectric effects, through coupling to the gain, cause interaction between sound waves which give rise to flux wave propagations. These waves travel at the velocity of sound and can have gain much larger than that of the ordinary peizoelectric waves. When the nonlinear mixing is taken into account, the mixing may be rapid enough to alter the collective wave to that of a second sound wave with velocity 1/√3 vs. The nonlinear mixing is examined, and it is proposed that the second sound conditions can only exist when a delicate balance is achieved between coherent gain and loss.