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Contrôle de la supraconductivité à l'interface d'oxydes LaAlO3/SrTiO3 par effet de champ électrique

Abstract : In this PhD work, we study the field-effect modulated two-dimensional superconductivity at the LaAlO3/SrTiO3 oxides hetero-interface. When one grows epitaxially a few unit cells thin film of LaAlO3 on a SrTiO3 substrate, the interface becomes conducting, and even superconducting below 300mK, although these two perovskite oxides are insulators. The properties of this high-mobility two-dimensional electron gas – superconductivity and strong Rashba-type spin-orbit coupling - can be field-effect modulated by the mean of a Back Gate. We have investigated this two-dimensional superconductivity through three different experimental approaches : the temperature-driven transition with the Berezinskii-Kosterlitz-Thouless model including an inhomogeneous distribution of rigidity ; the finite-size scaling analysis of the superconductor-to-insulator quantum phase transition induced by a perpendicular magnetic field using the model developed by Spivak, Oreto and Kivelson ; and finally the measure of the hysteretic and stochastic properties of the critical current in the framework of the RCSJ model. We hence propose to consider this 2D electron gas as an inhomogeneous network of superconducting puddles coupled to one another by Josephson effect through a normal metallic matrix, which transition is dominated by the XY model of the phase fluctuations. Finally, we demonstrated for the first time the possibility of Top Gated-control of this interface, and we investigated the compared effects of Top and Back Gating.
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  • HAL Id : tel-01132962, version 1

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Simon Hurand. Contrôle de la supraconductivité à l'interface d'oxydes LaAlO3/SrTiO3 par effet de champ électrique. Autre [cond-mat.other]. Université Pierre et Marie Curie - Paris VI, 2015. Français. ⟨NNT : 2015PA066014⟩. ⟨tel-01132962⟩

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