Interface physics of complex oxide heterostructures : Insights from x-ray spectroscopy
Vendredi 26 Avril 11h salle de réunion Bat.108 1er étage
Recent progress in epitaxial thin film growth of oxides, especially in Pulsed Laser Deposition (PLD), allows the preparation of oxide heterostructures with atomically sharp interfaces, opening promising perspectives for novel functionalities. A particular interesting situation arises, when an insulating polar oxide is combined with a non-polar one. In LaAlO3/SrTiO3 (LAO/STO), being the most prominent example of this kind, a high-mobility two-dimensional electron system (2DES) occurs in the interface, if the LAO layer exceeds a critical thickness [1,2]. While the precise microscopic origin of this interface phase is still under debate, the 2DES was observed to display fascinating properties, including its tunability by electrical gate fields, occurrence of superconductivity or even the coexistence of superconductivity and ferromagnetism.
Here I will discuss the interface physics of such heterostructures and show how x-ray based spectroscopies may provide valuable information on the electronic structure of such buried interfaces. This includes the atomic and orbital nature of the 2DES, its sheet carrier density and spatial extension , as well as the corresponding band dispersions and Fermi surface topology .
 A. Ohtomo et al., Nature 427, 423 (2004)
 S. Thiel et al., Science 313, 1942 (2006)  M. Sing et al., Phys. Rev. Lett. 102, 176805 (2009)
 G. Berner et al., submitted.
Work in collaboration with J. Mannhart (Stuttgart), G. Rijnders (Twente), M. Gorgoi (BESSY, Berlin), S. Suga (Osaka), Y. Saitoh (JAEA, Japan), Th. Kopp (Augsburg), and N. Pavlenko (Augsburg).