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Transport quantique dans les verres de spin

Abstract : The spin glass is a state of matter in which the magnetic disorder is quenched. Being considered as a model system for glasses in general, it has been extensively studied, both theoretically and experimentally. The research have converged towards two main descriptions of the fundamental state of the system that are clearly antagonist. On the one hand, the "mean-field" solution has a non trivial broken symmetry, and the ground state is composed of multiple valleys in a hierarchical structure. On the other hand, a magnetic "droplet" model, based on the off-equilibrium dynamics of a unique ground state. The experimental validation of one of these two theories requires a detailed observation of the sample at the microscopic level. Mesoscopic physics, which deals with interference effects of the electrons, proposes a unique tool to access to this microscopic configuration of the impurities: the universal conductance fluctuations. Indeed, these fluctuations represent a unique fingerprint of the sample disorder. This work presents the implementation of universal conductance fluctuations measurements in spin glasses. The electron interference effects being sensitive to the decoherence processes of the spin glass, they give access experimentally to new quantities related to the excitations of the system. The measurement of correlations between the disorder fingerprints allow to explore under a new perspective the non conventional order of this glassy state.
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Contributor : Thibaut Capron <>
Submitted on : Monday, April 9, 2012 - 10:18:17 PM
Last modification on : Friday, December 18, 2020 - 1:10:04 PM
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  • HAL Id : tel-00686330, version 1




Thibaut Capron. Transport quantique dans les verres de spin. Systèmes mésoscopiques et effet Hall quantique [cond-mat.mes-hall]. Université de Grenoble, 2011. Français. ⟨tel-00686330⟩



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