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Supraconducteurs mésoscopiques étudiés par microscopie tunnel à très basse température

Abstract : We study electronic effects of coherence that appear at very low temperature in non homogeneous superconductors. We have developed a Scanning Tunneling Microscope (STM) operating in a dilution fridge at a temperature of 60 mK. The resolution of the Local Density of States (LDOS) measured by the STM is 36 microeV. This is one of the best resolution obtained with this kind of system. We have studied proximity effects in junctions between a normal metal and a superconducting metal. In contrast with previous techniques, tunnel microscopy enables a continuous scan at the interface of the two metals. These measurements require specific sample shape (low relief, large field) and a good quality of metals (surface properties, transparency of the normal metal-superconductor interface). Providing these requirements, several sample fabrications have been developed. Each configuration exhibit its own tunnel measurement features. We
identify the limits and potentialities of this measurement method. We observed various types of spatial evolution of the LDOS depending on the geometry of metallic structures and the interface quality. These evolutions are in good agreement with Usadel equations that describe electron behaviour in presence of superconductivity in diffusive metals. These are the first STM measurements at very low temperature on samples processed by lithography.
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Submitted on : Saturday, November 4, 2006 - 9:55:28 AM
Last modification on : Friday, December 18, 2020 - 1:34:03 PM
Long-term archiving on: : Tuesday, April 6, 2010 - 7:04:07 PM

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  • HAL Id : tel-00111222, version 1

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UJF | CNRS | UGA

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Norbert Moussy. Supraconducteurs mésoscopiques étudiés par microscopie tunnel à très basse température. Supraconductivité [cond-mat.supr-con]. Université Joseph-Fourier - Grenoble I, 2000. Français. ⟨tel-00111222⟩

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