Quantum confinement in perovskite oxide heterostructures: tight binding instead of nearly free electron picture

TL;DR

This paper demonstrates that a tight binding model better explains quantum well states in perovskite oxide heterostructures with localized d electrons than the traditional nearly free electron approach.

Contribution

The authors develop simple first-principles tight binding models for perovskite oxide heterostructures, showing improved accuracy over NFE models for localized d-electron systems.

Findings

TB model provides a more reliable description of quantum well states.

Two-parameter TB models match experimental results more closely.

TB approach offers an intuitive physical understanding.

Abstract

Most recently, orbital-selective quantum well states of $d$ electrons have been experimentally observed in SrVO$_3$ ultrathin films [K. Yoshimatsu et. al., Science 333, 319 (2011)] and SrTiO$_3$ surfaces [A. F. Santander-Syro et. al., Nature 469, 189 (2011)]. Hitherto, one tries to explain these experiments by a nearly free electron (NFE) model, an approach widely used for delocalized electrons in semiconductor heterostructures and simple metal films. We show that a tight binding (TB) model is more suitable for describing heterostructures with more localized $d$ electrons. In this paper, we construct from first principles simple TB models for perovskite oxide heterostructures and surfaces. We show that the TB model provides a simple intuitive physical picture and yields, already with only two parameters, quantitatively much more reliable results, consistent with experiment.