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Quantum spin transport in paramagnetic systems

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dc.contributor.advisor David G. Cory and Leonid S. Levitov. en_US
dc.contributor.author Greenbaum, Daniel en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Physics. en_US
dc.date.accessioned 2006-03-29T18:42:45Z
dc.date.available 2006-03-29T18:42:45Z
dc.date.copyright 2005 en_US
dc.date.issued 2005 en_US
dc.identifier.uri http://hdl.handle.net/1721.1/32417
dc.description Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2005. en_US
dc.description Includes bibliographical references (p. 87-90). en_US
dc.description.abstract We have studied the transport of magnetization and energy in systems of spins 1/2 on a lattice at high temperature. This work was motivated by recent experiments which observed "spin diffusion" among the dipolar coupled nuclear spins of the insulator calcium fluoride, under conditions where it was appropriate to neglect the coupling to any heat reservoir. The dynamics under these conditions is coherent and reversible, yet signatures of irreversibility (i.e. diffusion) are typically observed. This state of affairs poses a formidable conceptual puzzle. In this thesis we present both phenomenological and microscopic models of spin diffusion, retaining the important aspects of statistical approaches to transport while incorporating relevant quantum effects. These methods allow an efficient calculation of energy diffusion for a long- range interaction, which has largely been an intractable problem. We study transport in two different limits, that where the XY term of the spin Hamiltonian is dominant, and that where it can be treated as a perturbation compared to the Ising term. In the case of dipolar couping, both limits are found to show slightly more rapid diffusion of inter spin energy than magnetization, in qualitative agreement with experiments. en_US
dc.description.statementofresponsibility by Daniel Greenbaum. en_US
dc.format.extent 90 p. en_US
dc.format.extent 3705976 bytes
dc.format.extent 3710254 bytes
dc.format.mimetype application/pdf
dc.format.mimetype application/pdf
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri http://dspace.mit.edu/handle/1721.1/7582
dc.subject Physics. en_US
dc.title Quantum spin transport in paramagnetic systems en_US
dc.type Thesis en_US
dc.description.degree Ph.D. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Physics. en_US
dc.identifier.oclc 61697858 en_US


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