Free carrier induced ferroelectricity in layered perovskites

TL;DR

This paper demonstrates that electron doping can enhance oxygen octahedral rotations in layered perovskites, enabling metallic ferroelectric-like phases through a novel design strategy involving hybrid-improper ferroelectrics.

Contribution

It introduces a new approach to induce ferroelectric-like behavior in metals by leveraging doping to strengthen octahedral rotations in hybrid-improper ferroelectrics.

Findings

Electron doping enhances oxygen octahedral rotations.

Predicted a metallic ferroelectric-like phase in a specific Ruddlesden-Popper compound.

Design strategy could enable new metallic ferroelectric materials.

Abstract

Doping ferroelectrics with carriers is often detrimental to polarization. This makes the design and discovery of metals that undergo a ferroelectric-like transition challenging. In this letter, we show from first principles that the oxygen octahedral rotations in perovskites are often enhanced by electron doping, and this can be used as a means to strengthen the structural polarization in certain hybrid-improper ferroelectrics -- compounds in which the polarization is not stabilized by the long range Coulomb interactions but is instead induced by a trilinear coupling to octahedral rotations. We use this design strategy to predict a cation ordered Ruddlesden-Popper compound that can be driven into a metallic ferroelectric-like phase via electrolyte gating.