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Systèmes de spins quantiques unidimensionnels. Désordre et impuretés

Abstract : This monography deals with three aspects of one dimensional condensed matter physics: the disordered spin 1 chain, non magnetic impurities in the spin 1/2 chain and reaction diffusion processes. We have studied the spin 1 chain under weak disorder with the abelian bosonisation and renormalisation group. This allows to take into account the competition between disorder and interactions and we predict the phase diagram of the anisotropic spin 1 chain. We predict the stability of the Haldane phase under weak disorder and the instability of the antiferromagnetic phase under random magnetic fields. The second part of this work deals with non magnetic impurities in spin 1/2 chains. These impurities are coupled to the edge of the chain and we predict the relaxation time of the nuclear spin of the impurities as a function of the temperature. This behaviour is different from the behaviour when the impurities are coupled to the bulk of the chain. The last part deals with reaction diffusion processes in one dimension. They can be reexpressed as quantum spin chains. We obtain a fermionic theory and deduce its critical exponents from the renormalisation group. Our new appraoch provide an alternative method to the epsilon expansion, and is in a reasonable agreement with numerical simulations.
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Contributor : Marc Gingold <>
Submitted on : Wednesday, November 28, 2001 - 11:13:14 AM
Last modification on : Wednesday, September 12, 2018 - 2:13:58 PM
Long-term archiving on: : Tuesday, September 11, 2012 - 1:10:21 PM


  • HAL Id : tel-00000893, version 1



Vivien Brunel. Systèmes de spins quantiques unidimensionnels. Désordre et impuretés. Physique mathématique [math-ph]. Université Paris Sud - Paris XI, 1999. Français. ⟨tel-00000893⟩



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