Chemical control of polar behavior in bicomponent short-period superlattices

TL;DR

This study uses first-principles calculations to explore how chemical composition influences polar behavior and ferroelectric properties in oxide superlattices with polar discontinuities, revealing off-centric movements and non-switchable polarizations.

Contribution

It demonstrates how chemical composition and polar interfaces affect ferroelectric distortions and polarization in oxide superlattices, highlighting the role of polar discontinuities and strain effects.

Findings

Polar discontinuities induce off-centric movements in ferroelectric layers.

Superlattices without polar discontinuities suppress off-centric movements.

Chemical composition and strain strongly influence ferroelectric behavior.

Abstract

Using first-principles density functional calculations, we study the interplay of ferroelectricity and polar discontinuities in a range of 1-1 oxide superlattices, built out of ferroelectric and paraelectric components. Studies have been carried out for a varied choice of chemical composition of the components. We find that, when polar interfaces are present, the polar discontinuities induce off- centric movements in the ferroelectric layers, even though the ferroelectric is only one unit cell thick. The distortions yield non-switchable polarizations, with magnitudes comparable to those of the corresponding bulk ferroelectrics. In contrast, in superlattices with no polar discontinuity at the interfaces, the off-centric movements in the ferroelectric layer are usually suppressed. The details of the behavior and functional properties are, however, found to be sensitive to epitaxial strain, rotational instabilities and second-order Jahn-Teller activity, and are therefore strongly in uenced by the chemical composition of the paraelectric layer.