Origin of the Two-Dimensional Electron Gas Carrier Density at theLaAlO3onSrTiO3Interface

Transport measurements of the two-dimensional electron gas at the ${\mathrm{LaAlO}}_3\mathrm{\text{−}}{\mathrm{SrTiO}}_3$ interface have found a density of carriers much lower than expected from the “polar catastrophe” arguments. From a detail density-functional study, we suggest how this discrepancy may be reconciled. We find that electrons occupy multiple subbands at the interface leading to a rich array of transport properties. Some electrons are confined to a single interfacial layer and susceptible to localization, while others with small masses and extended over several layers are expected to contribute to transport.