Modeling of resonant excitation of ferroelectric lattice subsystem by terahertz radiation under nonequilibrium conditions

Objectives . The search for a fundamentally new, fast, and least dissipative method for controlling the ferroic order parameter is a pressing and ambitious task of basic and applied research on the development of low-dissipation and high-speed functional elements of information systems operating at terahertz (THz) frequencies for 6G 2 network technologies. The aim of the work is to study the conditions for modulating ferroelectric polarization using a short THz pulse. This will also include the influence of additional factors on the efficiency of the THz-induced dynamics of the ferroic order parameter, such as stationary heating and the application of an additional electric field to the ferroelectric. Methods . The numerical simulation of resonant excitation of the lattice subsystem by THz radiation was performed for a Ba 0.8 Sr 0.2 TiO 3 ferroelectric film using the Landau–Khalatnikov equation system, and the equation of phonon mode oscillations with the phonon–phonon interaction as a driving force. The novelty of the proposed approach lies in the interaction of the THz pulse with a previously coherently excited phonon mode with a significant amplitude. Results . The time dependencies were presented for the polarization and the effective amplitude of infrared-active mode oscillations with varying THz field parameters. The results also included constants of expansion of the thermodynamic potential of the nonequilibrium state in powers of order parameter in various exposure modes, including temperature changes and the application of an additional external electric field. Conclusions . The approach proposed herein describes polarization switching under the action of a THz pulse with preliminary excitation of a coherent phonon by a femtosecond optical pulse. The most important parameter when determining the threshold effect of a THz pulse on phonon excitation is pulse energy (amplitude). In the region of small amplitudes, an increase in temperature does not exacerbate switching conditions.