# Strain-controlled Insulator-Metal Transition in YTiO3/SrTiO3 Superlattices: A First-Principles Study

## TL;DR

This study uses first-principles calculations to show that applying slight compressive strain induces an insulator-metal transition in YTiO3/SrTiO3 superlattices, linked to structural changes and electron redistribution.

## Contribution

It reveals the strain and electron correlation effects causing insulator-metal transitions in YTiO3/SrTiO3 superlattices, advancing understanding of their electronic phase control.

## Key findings

- Insulator-metal transition occurs at 0.2% compressive strain.
- Structural phase transition restores inversion symmetry.
- Reducing U from 5 to 4 eV also induces transition.

## Abstract

The structural, magnetic, and electronic properties of (STO)$_4$/(YTO)$_2$ superlattice consisting of Mott insulator YTiO$_3$ (YTO) and band insulator SrTiO$_3$ (STO) under strain are investigated by the density-functional-theory plus \emph{U} method. It is found that an insulator-metal transition occurs when a compressive strain of 0.2\% is applied. The structural analyses reveal that the presence of metallic state in such superlattices accompanies structural phase transition with restoring of inversion symmetry. Further study shows that this strain-induced structural transition makes the $d$ energy level of the interfacial Ti atoms of the YTO layer move upward due to the decreasing of the TiO$_{6}$ octahedral volume and induces the electron reconstruction in the whole superlattice systems. In addition, when the on-site interaction $U$ is changed from 5 to 4 eV, a similar insulator-metal transition also occurs in such superlattices due to the weakened electron correlation. These findings can improve our understanding of the insulator-metal transitions in such oxide superlattices.