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

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.

6 pages, 5 figures