Ferroelectricity-induced asymmetrical two-dimensional electron gas in superlattices consisteing of insulating GdTiO3 and ferroelectric BaTiO3

TL;DR

This study uses first principles calculations to show that ferroelectric BaTiO3 induces an asymmetrical two-dimensional electron gas in GdTiO3/BaTiO3 superlattices, affecting electronic states and magnetism with potential spintronics applications.

Contribution

It reveals how ferroelectric polarization induces asymmetrical electronic and magnetic properties in GdTiO3/BaTiO3 superlattices, a novel insight into interface engineering.

Findings

Middle Ti-O monolayer becomes metallic due to ferroelectricity.

Electronic states and magnetism differ from non-ferroelectric superlattices.

Potential for spintronics applications with unique asymmetrical 2DEG.

Abstract

Two-dimensional electron gas due to semiconductor interfaces can have high mobility and exhibits superconductivity, magnetism, and other exotic properties that are unexpected in constituent bulk materials. We study crystal structures, electronic states, and magnetism of short-period (BTO)$_m$/(GTO)$_2$ ($m$=2 and 4) superlattices consisting of ferroelectric BaTiO$_3$ (BTO) and ferrimagnetic insulating polar GdTiO$_3$ (GTO) by first principles calculations. Our investigation shows that the middle Ti-O monolayer in the GTO layer becomes metallic because the ferroelectricity in the insulating BTO layer induces an inhomogeneous electric field against the polarity-produced electric field in the GTO layer and thus differentially changes the d energy levels of the three Ti-O monolayers related with the GTO layer. Through avoiding electron reconstruction, the ferroelectric polarization also makes the electronic states and magnetism of two interfacial Ti-O monolayers become substantially different from those in the GTO/SrTiO$_3$ superlattices without ferroelectricity. Such superlattices are interesting for potential spintronics applications because of their unique asymmetrical two-dimensional electron-gas properties and possible useful spin-orbit effects.