First-principles study of electronic reconstructions of LaAlO3/SrTiO3 heterointerfaces and their variants

We present a first-principles study of the electronic structures and properties of ideal (atomically sharp) LaAlO3/SrTiO3 (001) heterointerfaces and their variants such as a different class of quantum well systems. We demonstrate the insulating-to-metallic transition as a function of the LaAlO3 film thickness in these systems. After the phase transition, we find that conduction electrons are bound to the n-type interface while holes diffuse away from the p-type interface and we explain this asymmetry in terms of a large hopping matrix element that is particular to the n-type interface. We build a tight-binding model based on these hopping matrix elements to illustrate how the conduction electron gas is bound to the n-type interface. Based on the "polar catastrophe" mechanism, we propose a different class of quantum wells at which we can manually control the spatial extent of the conduction electron gas. In addition, we develop a continuous model to unify the LaAlO3/SrTiO3 interfaces and quantum wells and predict the thickness dependence of sheet carrier densities of these systems. Finally, we study the external field effect on both LaAlO3/SrTiO3 interfaces and quantum well systems. Our systematic study of the electronic reconstruction of LaAlO3/SrTiO3 interfaces may serve as a guide to engineering transition-metal-oxide heterointerfaces.