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Etude des supraconducteurs à haute température critique par diffusion des neutrons

Abstract : Just over twenty years after the discovery of high temperature superconducting compounds (HTSC), the physics of these compounds remains unexplained. This thesis focuses on two of the many issues that have arisen concerning these compounds: the magnetic excitations spectrum in the superconducting phase of Bi2Sr2CaCu2O8+x (Bi-2212) and the nature of the pseudogap phase. Elastic and inelastic neutron scattering techniques are very appropriate tools to investigate these issues. Although Bi-2212 is the reference compound for charge spectroscopy techniques (STM, ARPES), it has been little studied using inelastic neutron scattering. Our study shows the existence of two spin modes with a dispersion that is compatible with that measured in YBa2Cu3O6+x. This study reveals the link between the energy of the magnetic excitations and the spatial distribution of the gap observed by STM. We studied the normal phase (also called pseudogap phase) of HTSC, which presents strong differences to the Fermi liquid theory. Following various theoretical approaches, we report a non-trivial magnetic order in the pseudogap phase of YBa2Cu3O6+x. The study of La2-xSrxCuO4 shows a magnetic response too, although that response is different from the one observed in YBa2Cu3O6+x.
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Submitted on : Monday, January 5, 2009 - 1:08:58 PM
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Benoît Fauqué. Etude des supraconducteurs à haute température critique par diffusion des neutrons. Supraconductivité [cond-mat.supr-con]. Université Paris Sud - Paris XI, 2007. Français. ⟨tel-00349921⟩

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