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Spectroscopie tunnel dans des films minces proche de la transition supraconducteur-isolant

Abstract : This thesis presents a scanning tunneling spectrocsopy study of thin disordered superconducting films close to the superconductor-insulator transition (SIT), namely titanium nitride and amorphous indium oxide films. In the superconducting phase, both films can be driven into an insulating state by increasing disorder or by applying a perpendicular magnetic field. Our tunneling spectroscopy study performed at a temperature of 50 mK revealed strong disorder-enhanced inhomogeneities of the superconducting gap, despite an homogeneous disorder. Close to the SIT, such inhomogeneities yield a picture of superconducting islands connected by Josephson coupling. Consequently, an applied magnetic field breaks these weak links and restores the underlying insulating states. This thesis presents also a study of the superconducting fluctuations regime above the critical temperature. Fluctuations broaden the superconducting transition of thin films and open a pseudogap in the one-electron density of states. In TiN films, we measured a strong pseudogag in a wide temperature range. This pseudogap is in good agreement with a superconducting fluctuation pseudogap combined with a disorder-enhanced Coulomb anomaly.
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Submitted on : Tuesday, November 18, 2008 - 2:49:33 PM
Last modification on : Thursday, March 7, 2019 - 5:00:03 PM
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Benjamin Sacépé. Spectroscopie tunnel dans des films minces proche de la transition supraconducteur-isolant. Supraconductivité [cond-mat.supr-con]. Université Joseph-Fourier - Grenoble I, 2007. Français. ⟨tel-00339647⟩

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