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Étude par microscopie/spectroscopie tunnel de la transition isolant/métal induite par pulses électriques dans GaTa4Se8

Abstract : In this PhD thesis, we have studied using scannng tunneling microscopy/spectroscopy the two main phenomena due to interactions between electrons : superconductivity and Mott Metal-Insulator transition. The study of the intercalated graphite CaC6 show that this superconductor is well described by conventionnal BCS theory with a zero temperature gap of 1.6 +/-0.2 meV, even if a small spectroscopic broadening suggest a weak anisotropy in the ab plane. The imaging of vortex lattice give for the coherence lenght extrapolated at zero temperature 38 nanometers. The main part of the manuscript is dedicated to the study of the Electric Pusle Insulator-Metal Transition in the weak Mott Insulator GaTa4Se8. The application of the electric pulse induces the formation of metallic zones in a insulating matrix in the bulk material. These observations provides a natural explanation for the phenomenological model used in transport measurements. The application of voltage sweeps during spectroscopic measurements trigger a local Insulator-Metal transition and for increased biases (V>1.0V), one can observe a inflation of the surface as an effect of the electric field. The study of electron doped compound Ga0,91Zn0,15Ta4Se8 show that if doping induce a metallicity, the transition induced by the electric pulse is closer to a bandwith controled transition rather than a doping controled transition. This manuscript set the question if this phenomena is intrinsic to GaTa4Se8, or general to the other weak Mott insulators.
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Submitted on : Thursday, July 1, 2010 - 2:19:02 PM
Last modification on : Wednesday, December 9, 2020 - 3:11:16 PM
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  • HAL Id : tel-00496843, version 1


Vincent Dubost. Étude par microscopie/spectroscopie tunnel de la transition isolant/métal induite par pulses électriques dans GaTa4Se8. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 2010. Français. ⟨tel-00496843⟩



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