Fundamental asymmetry in interfacial electronic reconstruction between insulating oxides: An ab initio study

We present an ab initio study of the (001) interfaces between two insulating perovskites, the polar LaAlO₃ and the nonpolar SrTiO₃. We observe an insulating-to-metallic transition above a critical LaAlO₃ thickness. We explain that the high conductivity observed at the TiO₂/LaO interface and the lack of similar conductivity at the SrO/AlO₂ interface are inherent in the atomic geometry of the system. A large interfacial hopping matrix element between cations causes the formation of a bound electron state at the TiO₂/LaO interface. This mechanism for the formation of interfacial bound states suggests a robust means for tuning conductivities at various oxide heterointerfaces.