Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 19: CE: Metal-Insulator Transition 2

TT 19.11: Talk

Wednesday, March 24, 2010, 12:30–12:45, H18

Microscopic origin of the electronic reconstruction at the LaAlO₃/SrTiO₃ interface — •Andrea Rubano¹, Domenico Paparo², Antigone Marino², Paolo Perna², Umberto Scotti di Uccio², Fabio Miletto Granozio², Christoph Richter³, Stefan Paetel³, Jochen Mannhart³, Lorenzo Marrucci², and Manfred Fiebig¹ — ¹HISKP, Universitaet Bonn, Bonn, Germany — ²CNR-INFM Coherentia and Dip. di Scienze Fisiche, Università di Napoli Federico II, Italy — ³Center for Electronic Correlations and Magnetism, Institute of Physics, University of Augsburg, Germany

LaAlO₃/SrTiO₃ interfaces are one of the most challenging topics in the field of perovskite oxides. Recently it was observed that a conductive two-dimensional electron gas (2DEG) emerges at the interface of these wide-gap insulators. The 2DEG formation occurs once n≥4 LaAlO₃ monolayers are deposited on top of the SrTiO₃. Although some macroscopic models have been proposed, our understanding on the microscopic scale is still at its infancy. Second harmonic (SHG) spectroscopy is an interface-only sensitive technique and, thus, an ideal tool to study these materials. Applying SHG, we demonstrate that a structural reorganization of the interfacial Ti-orbitals already occurs at n=3, yet without any onset of conductivity, because the injected carriers are localized at the interface. The electronic reorganization at n=3 leads to an abrupt increase of the SHG yield due to the enhancement of the polar asymmetry of the Ti 3d orbitals, and a crystal field splitting of the d(xy) orbitals is observed.