Ab-initio Low-Energy Model of Transition-Metal-Oxide Heterostructure LaAlO3/SrTiO3

TL;DR

This paper introduces a multi-scale ab-initio method to derive low-energy models for transition-metal-oxide heterostructures, enabling first-principles study of strongly correlated interface systems.

Contribution

The authors develop the MACE scheme to accurately determine low-energy effective models for oxide interfaces from first principles, separating entangled bands with cRPA.

Findings

Ti t2g on-site energies differ between layers by ~650 meV

Transfer integrals in the first layer resemble bulk SrTiO3

Screened Coulomb interactions increase by about 10% in the first layer

Abstract

We develop the multi-scale ab-initio scheme for correlated electrons (MACE) for transitionmetal-oxide heterostructures, and determine the parameters of the low-energy effective model. By separating Ti t2g bands near the Fermi level from the global Kohn-Sham (KS) bands of LaAlO3/SrTiO3 which are highly entangled with each other, we are able to calculate the parameters of the low-energy effective model of the interface with the help of constrained random phase approximation (cRPA). The on-site energies of the Ti t2g orbitals in the 1stlayer is about 650 meV lower than those in the 2nd-layer. In the 1st-layer, the transfer integral of the Ti t2g orbital is nearly the same as that of the bulk SrTiO3, while the effective screened Coulomb interaction becomes about 10 percent larger than that of the bulk SrTiO3. The differences of the parameters from the bulk SrTiO3 reduce rapidly with increasing distance from the interface. Our present versatile method makes it possible to derive effective ab-initio low-energy models and allows studying interfaces of strongly correlated electron systems from first principles.