Artificial quantum confinement in LAO3/STO heterostructure

TL;DR

This study investigates how varying the thickness of the STO layer in LAO/STO heterostructures affects the quantum confinement and electronic band structure of the interfacial 2D electron system using soft X-ray ARPES and ab-initio calculations.

Contribution

It demonstrates control over the quantum confinement and electronic structure of the 2DES by adjusting the STO layer thickness in heterostructures.

Findings

Varying STO thickness modifies the quantization of 3d t2g bands.

Charge distribution between dxy and dxz/dyz bands is affected by STO layer thickness.

The electronic structure can be tuned via heterostructure engineering.

Abstract

Heterostructures of transition metal oxides (TMO) perovskites represent an ideal platform to explore exotic phenomena involving the complex interplay between the spin, charge, orbital and lattice degrees of freedom available in these compounds. At the interface between such materials, this interplay can lead to phenomena that are present in none of the original constituents such as the formation of the interfacial 2D electron system (2DES) discovered at the LAO3/STO3 (LAO/STO) interface. In samples prepared by growing a LAO layer onto a STO substrate, the 2DES is confined in a band bending potential well, whose width is set by the interface charge density and the STO dielectric properties, and determines the electronic band structure. Growing LAO (2 nm) /STO (x nm)/LAO (2 nm) heterostructures on STO substrates allows us to control the extension of the confining potential of the top 2DES via the thickness of the STO layer. In such samples, we explore the dependence of the electronic structure on the width of the confining potential using soft X-ray ARPES combined with ab-initio calculations. The results indicate that varying the thickness of the STO film modifies the quantization of the 3d t2g bands and, interestingly, redistributes the charge between the dxy and dxz/dyz bands.