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Supraconductivité en présence de forts effets paramagnétique et spin-orbite

Abstract : The superconducting state being a Cooper pair condensate built on opposite spin and momentum electrons, it can be strongly influenced by any spin effect. In this thesis, we investigate the roles of strong paramagnetic and spin-orbit effects on superconducting properties. In a first part, the interplay between paramagnetic effect and bulk superconductivity is studied, leading to the modulated Fulde, Ferrell, Larkin and Ovchinnikov phase (FFLO phase). We focus on superconducting fluctuations near to the FFLO state. We show that these fluctuations can serve as asmoking gun for this phase. Noticeably, the fluctuation heat capacity and paraconductivity diverge in a characteristic way when approaching the phase transition towards a modulated state. Moreover, the fluctuation induced magnetization is predicted to be drastically quenched or to oscillate between dia- and para-magnetic responses. The second part is devoted to superconductor-ferromagnetic (S/F) junctions. In S/F/S Josephson junctions, the exchange field is responsible for the critical current oscillation, characterized by alternative 0- and π-states, with respect to the junction length. We predict a temperature induced (0 - π) state transition, even in the ballistic case. Moreover, the ballistic case exhibits some power law decays of the Josephson current, in contrast to the exponentially decaying current in dirty limit. The moderately dirty limit is then investigated, and the second harmonic of the current-phase relation is established. The last part deals with proximity effects when both paramagnetic and spin-orbit interactions are present in a Josephson junction. We show that the association of both Rashba interaction and exchange field induces a direct coupling between magnetic and superconducting orders. Particularly, this coupling generates the complete magnetization dynamics by applying an appropriate d.c. voltage.
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Contributor : François Konschelle <>
Submitted on : Wednesday, September 15, 2010 - 11:38:58 PM
Last modification on : Monday, January 22, 2018 - 11:02:02 AM
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François Konschelle. Supraconductivité en présence de forts effets paramagnétique et spin-orbite. Supraconductivité [cond-mat.supr-con]. Université Sciences et Technologies - Bordeaux I, 2009. Français. ⟨tel-00517920⟩

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