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Résumé :   Oxide materials display within the same family of compounds a variety of exciting electronic properties ranging from ferroelectricity to ferromagnetism and superconductivity. These systems are often characterized by strong electronic correlations, complex phase diagrams and competing ground states. This competition makes these materials electronic properties very sensitive to external parameters such as pressure or magnetic field. An interface, which naturally breaks inversion symmetry, is a major perturbation and one may thus expect that electronic systems with unusual properties can be generated at oxide interfaces [see for instance 1,2]. The numerous degrees of freedom in oxide materials (charge, spin, orbital, lattice) may lead at interfaces to novel ordering phenomena and electronic properties different from the ones of the bulk compounds. A striking example is the interface between LaAlO3 and SrTiO3, two good insulating perovskite oxides, which was found in 2004 to be conducting with a high mobility [3], and superconducting with a critical temperature of about 200 mK [4]. The characteristics observed for the superconducting transitions are consistent with a two-dimensional superconducting sheet a few nanometers thick. Recent field effect experiments revealed the sensitivity of the normal and superconducting states to the carrier density. In particular, the electric field allows the tuning of the critical temperature between 200 mK and 0 K and thus the on-off switching of superconductivity, revealing a complex phase diagram and a superconductor to insulator transition [5]. I will discuss the perspectives opened by this new field of research sometimes called “oxide interface engineering”.


[1] “When oxides meet face to face”. E. Dagotto, Science 318, 1076 (2007).

[2] “Enter the oxides”. J. Heber, Nature 459, 28 (2009).

[3] “A high mobility electron gas at the LaAlO3/SrTiO3 heterointerface”. A. Ohtomo, H. Y. Hwang, Nature 427, 423 (2004).

[4] “Superconducting interfaces between insulating oxides”. N. Reyren, S. Thiel, A. D. Caviglia, L. Fitting Kourkoutis, G. Hammerl, C. Richter, C. W. Schneider, T. Kopp, A.-S. Ruetschi, D. Jaccard, M. Gabay, D. A. Muller, J.-M. Triscone and J. Mannhart, Science 317, 1196 (2007).

[5] “Electric field control of the LaAlO3/SrTiO3 interface ground state”. A. Caviglia, S. Gariglio, N. Reyren, D. Jaccard, T. Schneider, M. Gabay, S. Thiel, G. Hammerl, J. Mannhart, and J.-M. Triscone, Nature 456, 624 (2008).

 

Biographie :

 

Contact : Prof. Jean-Marc TRISCONE Condensed Matter Physics Department, University of Geneva, 24 Quai E.-Ansermet, 1211 Geneva 4, Switzerland.

http://dpmc.unige.ch/gr_triscone/homepage.html