Wannier-based definition of layer polarizations in perovskite superlattices

TL;DR

This paper introduces a Wannier-based method to define and analyze layer polarizations in ferroelectric perovskite superlattices, enabling detailed insights into local polarization effects and interface phenomena.

Contribution

It adapts the Wannier function approach to compute layer-specific polarizations in layered insulators, enhancing analysis of complex oxide systems.

Findings

Layer polarizations can be computed and decomposed at the layer level.

Sublattice displacements significantly affect layer polarizations.

Local symmetry breaking at interfaces influences polarization properties.

Abstract

In insulators, the method of Marzari and Vanderbilt [Phys. Rev. B {\bf 56}, 12847 (1997)] can be used to generate maximally localized Wannier functions whose centers are related to the electronic polarization. In the case of layered insulators, this approach can be adapted to provide a natural definition of the local polarization associated with each layer, based on the locations of the nuclear charges and one-dimensional Wannier centers comprising each layer. Here, we use this approach to compute and analyze layer polarizations of ferroelectric perovskite superlattices, including changes in layer polarizations induced by sublattice displacements (i.e., layer-decomposed Born effective charges) and local symmetry breaking at the interfaces. The method provides a powerful tool for analyzing the polarization-related properties of complex layered oxide systems.