Toroidal ferroelectricity in PbTiO3 nanoparticles

TL;DR

This study demonstrates that PbTiO3 nanoparticles can exhibit stable ferroelectricity through toroidal ordering, with size and shape influencing the polarization topology, which is promising for nanoscale device applications.

Contribution

First-principles-based simulations reveal size and shape effects on ferroelectricity and polarization topology in PbTiO3 nanoparticles, introducing a new ferroelectric bubble state.

Findings

Ferroelectricity persists in small PbTiO3 nanoparticles due to toroidal ordering.

Size and aspect ratio induce topological polarization transformations.

Ferroelectric bubble states are thermally stable and suitable for nanodevices.

Abstract

We report from first-principles-based atomistic simulations that ferroelectricity can be sustained in PbTiO3 nanoparticles of only a few lattice constants in size as a result of a toroidal ordering. We found that size-induced topological transformations lead to the stabilization of a ferroelectric bubble by the alignment of vortex cores along a closed path. These transformations, which are driven by the aspect ratio of the nanostructure, change the topology of the polarization field, producing a rich variety of polar configurations. For sufficiently flat nanostructures, a multi-bubble state bridges the gap between 0D nanodots and 2D ultra-thin films. The thermal properties of the ferroelectric bubbles indicate that this state is suitable for the development of nanometric devices.