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1	Transport électronique et Verres de Spins Paulin, Guillaume 22 June 2010 (has links) (PDF) The results reported in this thesis contribute to the understanding of disordered systems, to mesoscopic physics on the one hand, and to the physics of spin glasses on the other hand. The first part of this thesis studies numerically coherent electronic transport in a non magnetic metal accurately doped with frozen magnetic impurities (a low temperature spin glass). Thanks to a recursive code that calculates the two terminal conductance of the system, we study in detail the metallic regime of conduction (large conductance) as well as the insulating regime (small conductance). In both regimes, we highlight a universal behavior of the system. Moreover, a study of correlations between the conductance of different spin configurations of impurities allows us to link these correlations with correlations between spin configurations. This study opens the route for the first experimental determination of the overlap via transport measurements. A second part of this thesis deals with the study of the mean field Sherrington-Kirkpatrick model, which describes the low temperature phase of an Ising spin glass. We are interested here in the generalization of this model to quantum spins (i.e including the possibility to flip by quantum tunneling) of this classical model that was well studied during the past thirty years. We deduce analytically motion equations at the semi-classical level, for which the influence of quantum tunneling is weak, and we compare them with the classical case. We finally solve numerically these equations using a pseudo-spectral method. Mesoscopic Physics Coherent Electronic Transport Weak Localization Universal Conductance Fluctuations Disordered Systems Spin Glasses Spin Overlap Sherrington-Kirkpatrick model Quantum Fluctuations Replica Theory
2	Aggregation and Gelation in Random Networks / Aggregation und Gelation in zufälligen Netzwerken Ulrich, Stephan 03 March 2010 (has links) No description available. 530 Physik Mathematics and Computer Science Aggregation Elastizität Gelationsübergang Gele Gerichtete Polymere Granulate Nanokristalline Materialien Perkolation Polymere Replika-Theorie Röntgenstreuung Spinnenseide Thermodynamik Ungeordnete Festkörper Zufällige Netzwerke Aggregation Directed Polymers Disordered Solids Elasticity Gelation Transition Gels Granular Materials Nanocrystalline materials Percolation Polymers Random Networks Replica Theory Spider Silk Thermodynamics X-ray diffraction 33.25 33.62 RVM 210: Pulver Körner {Physik: Sonstige feste Stoffe}

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Transport électronique et Verres de Spins

Aggregation and Gelation in Random Networks / Aggregation und Gelation in zufälligen Netzwerken