Ultrasonic attenuation in superionic conductors

The ultrasonic attenuation and change of sound velocity caused by hopping particles are theoretically investigated. The piezoelectric and deformation potential couplings between particles and elastic waves are examined where the self-consistent electric field, and hence the density wave modulation of hopping particles, plays an important role. It turns out in systems with double-well potential that there exists a region where the sound velocity changes approximately between T and ln T. Huberman and Martin's type of attenuation in the absence of the modulation of the density wave is also derived in terms of configuration-dependent local potentials.