Berlin 2008 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 28: Correlated Electrons: Metal-Insulator Transition 1

TT 28.1: Talk

Thursday, February 28, 2008, 09:30–09:45, H 2053

Surface Effects on Oxide Heterostructures — •Cosima Schuster and Udo Schwingenschlögl — Institut für Physik, Universität Augsburg, D-86135 Augsburg

Perovskite heterostructures have attracted recent interest due to the discovery of metallic interlayers in an otherwise insulating structure. The physical properties of such a multilayer structure hence are not present in either of its constituents. For example, at the contact between the two band insulators LaAlO₃ and SrTiO₃ a quasi 2D electron gas with very high carrier density is formed. However, it was shown that the LaAlO₃ surface layer must reach a critical thickness of 4 unit cells for the interface to be conducting.

We report on surface effects on the electronic properties of interfaces in epitaxial LaAlO₃/SrTiO₃ heterostructures. Our results are based on DFT calculations for well-relaxed multilayer configurations, terminated by a thin 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.