Observation of Antiferroelectric Domain Walls in a Uniaxial Hyperferroelectric

TL;DR

This study reports the discovery of antiferroelectric domain walls in a uniaxial hyperferroelectric material, revealing highly mobile walls with unique dipole configurations and expanding the understanding of domain wall phenomena beyond ferroelectricity.

Contribution

The paper presents the first observation of antiferroelectric domain walls in a hyperferroelectric, supported by density functional theory, highlighting a new excited domain-wall state with potential for novel electronic properties.

Findings

Antiferroelectric domain walls are highly mobile and involve 180° dipole flips.

Pb$_{5}$Ge$_{3}$O$_{11}$ is identified as a hyperferroelectric material.

Antiferroelectric walls are energetically more costly than basic domain walls.

Abstract

Ferroelectric domain walls are a rich source of emergent electronic properties and unusual polar order. Recent studies showed that the configuration of ferroelectric walls can go well beyond the conventional Ising-type structure. N\'eel-, Bloch-, and vortex-like polar patterns have been observed, displaying strong similarities with the spin textures at magnetic domain walls. Here, we report the discovery of antiferroelectric domain walls in the uniaxial ferroelectric Pb$_{5}$Ge$_{3}$O$_{11}$. We resolve highly mobile domain walls with an alternating displacement of Pb atoms, resulting in a cyclic 180$^{\circ}$ flip of dipole direction within the wall. Density functional theory calculations reveal that Pb$_{5}$Ge$_{3}$O$_{11}$ is hyperferroelectric, allowing the system to overcome the depolarization fields that usually suppress antiparallel ordering of dipoles along the longitudinal direction. Interestingly, the antiferroelectric walls observed under the electron beam are energetically more costly than basic head-to-head or tail-to-tail walls. The results suggest a new type of excited domain-wall state, expanding previous studies on ferroelectric domain walls into the realm of antiferroic phenomena.