Ferroelectric PbTiO$_{3}$/SrRuO$_{3}$ superlattices with broken inversion symmetry

TL;DR

This study fabricates PbTiO$_{3}$/SrRuO$_{3}$ superlattices with ultra-thin layers, revealing controllable anisotropic electrical properties and polarization asymmetry due to inversion symmetry breaking, expanding the understanding of ferroelectric superlattices.

Contribution

It introduces a new class of ferroelectric superlattices with broken inversion symmetry, combining experimental and theoretical methods to explore their complex phase behavior.

Findings

Large electrical resistivity anisotropy controllable by layer thickness

Polarization asymmetry increases with reduced PbTiO$_{3}$ concentration

Demonstration of compositional inversion symmetry breaking in bi-color superlattices

Abstract

We have fabricated PbTiO$_{3}$/SrRuO$_{3}$ superlattices with ultra-thin SrRuO$_{3}$ layers. Due to the superlattice geometry, the samples show a large anisotropy in their electrical resistivity, which can be controlled by changing the thickness of the PbTiO$_{3}$ layers. Therefore, along the ferroelectric direction, SrRuO$_{3}$ layers can act as dielectric, rather than metallic, elements. We show that, by reducing the concentration of PbTiO$_{3}$, an increasingly important effect of polarization asymmetry due to compositional inversion symmetry breaking occurs. The results are significant as they represent a new class of ferroelectric superlattices, with a rich and complex phase diagram. By expanding our set of materials we are able to introduce new behaviors that can only occur when one of the materials is not a perovskite titanate. Here, compositional inversion symmetry breaking in bi-color superlattices, due to the combined variation of A and B site ions within the superlattice, is demonstrated using a combination of experimental measurements and first principles density functional theory.