Phonon radiation mechanism of electromagnetic wave in piezoelectric resonators

Piezoelectric mechanical antennas, whose core components are piezoelectric resonators, present disruptive potential as a promising alternative of traditional electric antennas for long-distance, underground, and underwater communications. However, the microscopic mechanism of the phonon radiation related to the oscillation of electric dipoles in piezoelectric resonators is still vague, hindering the fabrication of high-performance piezoelectric mechanical antennas. Here, we demonstrate the phonon radiation process at radio frequency in the piezoelectric perovskite via a microscopic model based on first-principles calculations. In this microscopic model, a dynamic fluctuation term arising under resonant conditions is introduced and treated within an oscillator-energy approximation. The time-dependent behavior of polarization and strain during resonance are then captured by numerically evaluating the equilibrium state. The microscopic model can quantify the coupled evolution of polarization and strain, as well as the resonance frequency and the radiation intensity, for arbitrary resonator dimensions under different temperatures and electric-field amplitudes. Our model successfully simulates the phonon radiation in the piezoelectric resonator, paving the way for the theoretical design of portable piezoelectric resonators in next-generation piezoelectric mechanical antennas.