On a new type of surface acoustoelectric waves in hexagonal crystals

It is shown that, in the basal plane of crystals with hexagonal symmetry, purely longitudinal surface acoustoelectric waves can propagate. In contrast to well-known Gulyaev-Blustein transverse waves, these longitudinal waves are localized in the surface layer, whose thickness is on the order of the wavelength. The field of mechanical displacements and the potential field of the wave are phase shifted by ??/2. The electricfield vector of the wave is circularly polarized in the sagittal plane.