Theory of Mott insulator/band insulator heterostructure

TL;DR

This paper develops a theoretical model for LaTiO₃/SrTiO₃ heterostructures, analyzing their electronic phases, charge distribution, and optical properties, revealing that heterostructure edges are typically metallic.

Contribution

It introduces a comprehensive theoretical framework combining tight-binding, Hartree, and Hartree-Fock methods to study Mott/band insulator heterostructures and predicts their phase behavior and edge metallicity.

Findings

Heterostructure edges are generally metallic.

Phase diagram depends on interaction strength and layer number.

Predictions for optical conductivity experiments.

Abstract

A theory of heterostructures comprised of LaTiO$_3$ (a Mott insulator) and SrTiO$_3$ (a band insulator) is presented. The band structure of the Ti $d$% -electrons is treated with a nearest neighbor tight-binding approximation; the electric fields arising from the La$^{3+}$/Sr$^{2+}$ charge difference and the carriers are treated within a Hartree approximation; and the on-site interactions are treated by unrestricted Hartree-Fock. The phase diagram as a function of interaction strength and layer number is determined and predictions are made for optical conductivity experiments. A note worthy finding is that the edges of the heterostructure are generally metallic.