Meta-screening and permanence of polar distortion in metallized ferroelectrics

TL;DR

This study uses first-principles simulations to show that polar distortions in ferroelectrics generally resist becoming metallic, with a meta-screening effect explaining the persistence of non-centrosymmetric phases in doped compounds.

Contribution

It reveals the meta-screening effect as key to maintaining polar distortions in metallized ferroelectrics, advancing understanding of structurally-polar metals.

Findings

Polar distortion resists metallization in most ferroelectrics.

Meta-screening due to charge rearrangements supports non-centrosymmetric phases.

Guidelines for ferroelectric behavior near conductive elements.

Abstract

Ferroelectric materials are characterized by a spontaneous polar distortion. The behavior of such distortions in the presence of free charge is the key to the physics of metallized ferroelectrics in particular, and of structurally-polar metals more generally. Using first-principles simulations, here we show that a polar distortion resists metallization and the attendant suppression of long-range dipolar interactions in the vast majority of a sample of 11 representative ferroelectrics. We identify a meta-screening effect, occurring in the doped compounds as a consequence of the charge rearrangements associated to electrostatic screening, as the main factor determining the survival of a non-centrosymmetric phase. Our findings advance greatly our understanding of the essentials of structurally-polar metals, and offer guidelines on the behavior of ferroelectrics upon field-effect charge injection or proximity to conductive device elements.