Many-body and Covalence Effects in the Polarization of Ferroelectric Perovskites

TL;DR

This paper investigates the large ferroelectric polarization in perovskite oxides, revealing the roles of covalence and electron-electron interactions through advanced quantum calculations, and identifies a transition from band to Mott insulator affecting polarization.

Contribution

It introduces an explicitly correlated scheme and geometric quantum phase approach to analyze polarization, highlighting the effects of covalence and electron interactions in perovskites.

Findings

Electron-electron interactions enhance polarization in weakly correlated regimes.

A transition from band insulator to Mott insulator causes a discontinuous change in polarization.

Oxygen transport of positive charge occurs above the Mott transition.

Abstract

The ferroelectric polarization of perovskite oxides is much larger than implied by displacement of static ionic charges. We use an explicitly correlated scheme to investigate the phenomenon; charge transport is evaluated as a geometric quantum phase. Both covalence and electron-electron interaction enhance polarization in the weakly correlated regime. At higher values of the electron-electron interaction, the system undergoes a transition from a band insulator to a Mott insulator: the static ionic charge is continuous across the transition, whereas the polarization is discontinuous. Above the transition, oxygen transports a positive charge.