The Mott insulator LaTiO_3 in heterostructures with SrTiO_3 is metallic

TL;DR

This study demonstrates that LaTiO_3 in heterostructures with SrTiO_3 is a strongly correlated metal rather than a Mott insulator, due to lattice geometry effects that alter electronic interactions.

Contribution

It reveals that the metallic behavior in LaTiO_3/SrTiO_3 heterostructures arises from lattice-induced electronic structure changes, not interface effects, using dynamical mean field theory.

Findings

LaTiO_3 becomes metallic in heterostructures with SrTiO_3

Lattice geometry influences the electronic band width and crystal field

Local Coulomb interactions are insufficient for a Mott transition

Abstract

It is shown that LaTiO_3 in superlattices with SrTiO_3 is not a Mott insulator but a strongly correlated metal. The tetragonal lattice geometry imposed by the SrTiO_3 substrate leads to an increase of the Ti 3d t2g band width and a reversal of the t2g crystal field relative to the orthorhombic bulk geometry. Using dynamical mean field theory based on finite-temperature multi-band exact diagonalization we show that, as a result of these effects, local Coulomb interactions are not strong enough to induce a Mott transition in tetragonal LaTiO_3. The metalicity of these heterostructures is therefore not an interface property but stems from all LaTiO_3 planes.