# Superlattice-induced ferroelectricity in charge-ordered La$_{1/3}$Sr$_{2/3}$FeO$_{3}$

## TL;DR

This study demonstrates that artificial structuring of La$_{1/3}$Sr$_{2/3}$FeO$_{3}$ induces a ferroelectric charge-ordered phase with significant polarization, highlighting a new pathway for high-frequency, electron-driven ferroelectric materials.

## Contribution

The paper shows that superlattice structuring of LSFO induces charge-order-driven ferroelectricity, a novel approach for designing functional ferroelectric materials.

## Key findings

- Artificial layering breaks inversion symmetry in LSFO.
- The ferroelectric phase has a polarization of 39 μC/cm$^2$.
- Charge transfer between Fe ions underpins the ferroelectricity.

## Abstract

Charge-order-driven ferroelectrics are an emerging class of functional materials, distinct from conventional ferroelectrics, where electron-dominated switching can occur at high frequency. Despite their promise, only a few systems exhibiting this behavior have been experimentally realized thus far, motivating the need for new materials. Here, we use density functional theory to study the effect of artificial structuring on mixed-valence solid-solution La$_{1/3}$Sr$_{2/3}$FeO$_{3}$ (LSFO), a system well-studied experimentally. Our calculations show that A-site cation (111)-layered LSFO exhibits a ferroelectric charge-ordered phase in which inversion symmetry is broken by changing the registry of the charge order with respect to the superlattice layering. The phase is energetically degenerate with a ground-state centrosymmetric phase, and the computed switching polarization is 39 $\mu$C/cm$^{2}$, a significant value arising from electron transfer between Fe ions. Our calculations reveal that artificial structuring of LSFO and other mixed valence oxides with robust charge ordering in the solid solution phase can lead to charge-order-induced ferroelectricity.