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Spectroscopie locale à basse température dans des systèmes supraconducteurs désordonnés

Abstract : This thesis presents a study combining tunneling spectroscopy, point-contact Andreev spectroscopy and electronic transport on disordered superconducting indium oxide samples. Transport measurements reveal a diverging resistivity from room temperature shortcut by superconductivity at low temperature. This behavior shows that our samples are in the vicinity of the metal-insulator Anderson transition. Tunneling spectroscopy highlights a rather unusual superconducting state with a pseudogap regime above the critical temperature. It evolves at low temperature into an inhomogeneous system composed of both superconducting Cooper pairs and Cooper pairs without phase coherence, localized by the disorder. Comparison between different samples shows that incoherent Cooper pairs proliferate with increasing level of disorder, what indicates that superconductor-insulator transition in indium oxide is governed by the progressive localization of Cooper pairs. Besides, using our STM, we have continuously analyzed the local conductance between tunneling regime and contact regime. Andreev spectroscopy thus reveals a new energy scale related to the superconducting phase coherence and independent from spatial fluctuations of the density of states measured in tunneling regime. This shows that disorder induces a dichotomy between the pairing energy characterizing the binding of electrons into pairs and the coherence energy specific to macroscopic superconductivity.
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https://tel.archives-ouvertes.fr/tel-00576226
Contributor : Thomas Dubouchet <>
Submitted on : Sunday, March 13, 2011 - 7:07:20 PM
Last modification on : Wednesday, November 4, 2020 - 2:46:40 PM
Long-term archiving on: : Tuesday, June 14, 2011 - 2:34:06 AM

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  • HAL Id : tel-00576226, version 1

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Thomas Dubouchet. Spectroscopie locale à basse température dans des systèmes supraconducteurs désordonnés. Physique [physics]. Université de Grenoble, 2010. Français. ⟨tel-00576226⟩

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