Domain Wall Acceleration by Ultrafast Field Application: An Ab Initio‐Based Molecular Dynamics Study

Abstract

Optimizing ferroelectrics for contemporary high‐frequency applications asks for the fundamental understanding of ferroelectric switching and domain wall (DW) motion in ultrafast field pulses while the microscopic understanding of the latter is so far incomplete. To close this gap in knowledge, ab initio‐based molecular dynamics simulations are utilized to analyze the dynamics of 180° DWs in the prototypical ferroelectric material BaTiO3. How ultrafast field application initially excites the dipoles in the system and how they relax to their steady state via transient negative capacitance are discussed. Excitingly, a giant boost of the DW velocity related to the nonequilibrium switching of local dipoles acting as nucleation centers for the wall movement is found. This boost may allow to tune the local ferroelectric switching rate by the shape of an applied field pulse.

Influence of domain walls and defects on the electrocaloric effect

“…In both cases, the mean polarization per layer along the y-direction ⟨p b ⟩ x changes sign across the walls. We initialize these walls by the pre-poling protocol from reference [38] i.e. thermalization of the system at a given temperature using the Nosé-Poincaré thermostat [49] under applied local fields, which are then successively removed.…”

“…In this paper, we study the adiabatic field response of multi-domain FEs in combination with symmetry conforming defect dipoles and the phase boundary between two FE phases. We use BaTiO 3 as a model system, as its phase and domain structure [12,35] and DW dynamics [36][37][38] are well established and as its experimental FE-FE phase transition from tetragonal (T) to orthorhombic (O) phase at 5 • C occurs at a suitable temperature range for applications. To separate the different effects, we first include only DWs and calculate the field response in the T and O phases.…”