Electronic Structure of Oxide Interfaces: A Comparative Analysis of GdTiO${}_3$/SrTiO${}_3$ and LaAlO${}_3$/SrTiO${}_3$ Interfaces

Abstract

Emergent phases in the two-dimensional electron gas (2DEG) formed at the interface between two insulating oxides have attracted great attention in the past decade. We present ab-initio electronic structure calculations for the interface between a Mott insulator GdTiO${}_3$ (GTO) and a band insulator SrTiO${}_3$ (STO) and compare our results with those for the widely studied LaAlO${}_3$/SrTiO${}_3$ (LAO/STO) interface between two band insulators. Our GTO/STO results are in excellent agreement with experiments, but qualitatively different from LAO/STO. We find an interface carrier density of 0.5$e^{-}$/Ti, independent of GTO thickness in both superlattice and thin film geometries, in contrast to LAO/STO. The superlattice geometry in LAO/STO offers qualitatively the same result as in GTO/STO. On the other hand, for a thin film geometry, the interface carrier density builds up only beyond a threshold thickness of LAO. The positive charge at the vacuum surface that compensates the 2DEG at the interface also exhibits distinct behaviors in the two systems. The top GTO layer is found to be insulating due to correlation-driven charge disproportionation, while the top LAO layer is metallic within band theory and may become insulating due to surface disorder or surface reconstruction.

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References in corpus (7)

• Magnetic effects at the interface between nonmagnetic oxides
• Origin of charge density at LaAlO3-on-SrTiO3 hetero-interfaces; possibility of intrinsic doping
• Avoiding the polarization catastrophe in LaAlO3 overlayers on SrTiO3(001) through a polar distortion
• Carrier-controlled ferromagnetism in SrTiO3
• Electronic structure induced reconstruction and magnetic ordering at the LaAlO${}_3|$SrTiO${}_3$ interface
• Dimer Mott Insulator in an Oxide Heterostructure
• Microscopic model for transitions from Mott to spin-Peierls insulator in TiOCl

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