Terahertz oscillation of $180^{\circ}$ domain walls in ferroelectric membranes

TL;DR

This paper uses phase-field simulations and analytical modeling to discover and analyze a novel terahertz-frequency domain wall sliding mode in ferroelectric BaTiO3 membranes, revealing strain-dependent control of high-frequency DW dynamics.

Contribution

It identifies a new DW sliding mode with a nonzero resonant frequency driven by depolarization fields, and develops an analytical model to predict strain effects on this mode.

Findings

Discovered a unique terahertz DW sliding mode with dynamic internal structure.

Validated strain dependence of mode frequencies through simulations and analytical model.

Proposed applications in reconfigurable THz and optical devices.

Abstract

A fundamentally intriguing yet not well understood topic in the field of ferroelectrics is the collective excitation of domain walls (DWs), with potential applications to DW-based nanoelectronic and optoelectronic devices. Here we use dynamical phase-field simulations to identify the collective modes of an Ising-type $180^{\circ}$ DW in a uniaxially strained BaTiO3 membrane. The membrane concurrently functions as a cavity for polarization and acoustic waves and permits cavity-enhanced resonant excitation of polarization waves. The simulation reveals an unconventional DW sliding mode that exhibits a depolarization-field-driven nonzero resonant frequency and a dynamically changing internal structure during sliding. These features differ from the previously reported DW sliding modes that have a zero resonant frequency or a rigid internal structure. An analytical model is developed to quantitatively understand the origin of this new DW mode and predict the effect of strain on the mode frequency. The analytically predicted strain dependence of the frequencies of the unconventional DW sliding mode and the DW breathing mode, both in the terahertz regime, is further validated by dynamical phase-field simulations. These results provide new insights into the high-frequency dynamics of ferroelectric DWs and suggest opportunities for realizing on-demand control of phonon-DW resonance by strain, and more broadly, discovering and controlling unconventional DW modes in conventional domain patterns, with applications to reconfigurable THz and optical devices.