Strain and composition dependence of the orbital polarization in nickelate superlattices

TL;DR

This study investigates how strain and chemical composition influence orbital polarization in nickelate superlattices, revealing strain as the dominant control parameter for polarization levels up to 25%.

Contribution

It provides a quantitative analysis separating the effects of strain and composition on orbital polarization in nickelate superlattices.

Findings

Orbital polarization reaches up to 25%.

Strain is the primary factor influencing polarization.

Chemical composition has a smaller effect.

Abstract

A combined analysis of x-ray absorption and resonant reflectivity data was used to obtain the orbital polarization profiles of superlattices composed of four-unit-cell-thick layers of metallic LaNiO3 and layers of insulating RXO3 (R=La, Gd, Dy and X=Al, Ga, Sc), grown on substrates that impose either compressive or tensile strain. This superlattice geometry allowed us to partly separate the influence of epitaxial strain from interfacial effects controlled by the chemical composition of the insulating blocking layers. Our quantitative analysis reveal orbital polarizations up to 25%. We further show that strain is the most effective control parameter, whereas the influence of the chemical composition of the blocking layers is comparatively small.