Abstract
We report on surface effects on the electronic properties of interfaces in epitaxial LaAlO3/SrTiO3 heterostructures. Our results are based on first-principles electronic structure calculations for well-relaxed multilayer configurations, terminated by an ultrathin LaAlO3 surface layer. On varying the thickness of this layer, we find that the interface conduction states are subject to almost rigid band shifts due to a modified Fermi energy. Confirming experimental data, the electronic properties of heterointerfaces therefore can be tuned systematically by alterating the surface-interface distance. We expect that this mechanism is very general and applies to most oxide heterostructures.