Engineering Correlation Effects via Artificially Designed Oxide Superlattices

TL;DR

This paper uses ab initio calculations to design oxide superlattices that exhibit novel correlation effects, leading to a new type of Mott insulator with potential for tunable electronic properties.

Contribution

It introduces a new superlattice design of LaTiO3 and LaNiO3 that exhibits a S=1 Mott insulating state with unique charge transfer and magnetic properties.

Findings

Identified a superlattice as a S=1 Mott insulator with large Ni magnetic moments.

Demonstrated charge transfer gap driven by Ni d and Ti d state differences.

Showed doping induces a single-band electronic structure with antiferromagnetic correlations.

Abstract

Ab initio calculations are used to predict that a superlattice composed of layers of LaTiO3 and LaNiO3 alternating along the [001] direction is a S=1 Mott insulator with large magnetic moments on the Ni sites, negligible moments on the Ti sites and a charge transfer gap set by the energy difference between Ni d and Ti d states, distinct from conventional Mott insulators. Correlation effects are enhanced on the Ni sites via filling the oxygen p states and reducing the Ni-O-Ni bond angle. Small hole (electron) doping of the superlattice leads to a two-dimensional single-band situation with holes (electrons) residing on Ni dx2-y2 (Ti dxy) orbital and coupled to antiferromagnetically correlated spins in the NiO2 layer.