Acoustic Gain in Solids due to Piezoelectricity, Flexoelectricity, and Electrostriction

Abstract

A quantitative discussion of the combined influence of three electro mechanical effects: piezoelectricity, flexoelectricity, and electrostriction in solids is provided for acoustic absorption and gain. While piezoelec tricity occurs in noncentrosymmetric materials only, flexoelectricity and electrostriction exist in all materials. Two important new results are dem onstrated: 1) the possibility to realize acoustic gain in all materials (cen trosymmetric and noncentrosymmetric) when the acoustic Cherenkov condition is fulfilled, and 2) realization of acoustic gain in the presence of a strong dc electric field, even when the Cherenkov condition is not fulfilled, in the case of strong crosscoupling between piezoelectricity, flexoelec tricity, and electrostriction. A simple analytical expression for the acoustic dispersion relation is derived for the combined effect of piezoelectricity, flexoelectricity, and electrostriction. At lower frequencies, the piezoelectric effect dominates for inversionasymmetric materials. At high frequencies (≈>1 MHz) flexoelectricity becomes increasingly important and eventually provides a major mechanism for gain and absorption in barium titanate (BaTiO 3). In the presence of strong electric fields (≈>1 MV m −1), electrostric tion provides a dominant isolated contribution to absorption/gain in BaTiO 3. Strong coupling between the three electromechanical contributions determines the total absorption/gain coefficient.

Acoustic coherent perfect absorber and laser modes via the non-Hermitian dopant in the zero index metamaterials

“…required. 31,32 However, an acoustic gain medium can hardly be obtained naturally, but with the knowledge of active control 33 or electromechanical effects, 34 the acoustic gain effect can be experimentally observed through an elaborate design. Also, these active elements have their own dynamic ranges that can be adjusted for the input signals.…”

Anomalous Topological Edge States in Non-Hermitian Piezophononic Media

“…We numerically employ piezoelectric semiconductors which, when electrically biased, generate a nonreciprocal response owing to the acoustoelectric effect. Thanks to the intrinsic electron-phonon interaction, sound amplification or attenuation is taking place in response to an appropriately applied electric field, which is interesting for various appealing applications [27][28][29][30]. Thus, this accessible piezophononic platform is employed to mimic the non-Hermitian Su-Schrieffer-Heeger (SSH) model [21,31] for mechanical vibrations.…”