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Perturbation theory by flow equations: dimerized and frustrated S = 1/2 chain

  • C. Knetter
  • G.S. Uhrig

Abstract:

The flow equation method (Wegner, 1994) is used as continuous unitary transformation to construct perturbatively effective Hamiltonians. The method is illustrated in detail for dimerized and frustrated antiferromagnetic S=1/2 chains. The effective Hamiltonians conserve the number of elementary excitations which are S=1 magnons for the dimerized chains. The sectors of different number of excitations are clearly separated. Easy-to-use results for the gap, the dispersion and the ground state energies of the chains are provided.

PACS. 75.10.Jm Quantized spin models – 02.30.Mv Approximations and expansions – 03.65.-w Quantum mechanics 

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© EDP Sciences, Springer-Verlag, Società Italian a di

Authors and Affiliations

  • C. Knetter
    • 1
  • G.S. Uhrig
    • 1
  1. 1.Institut für Theoretische Physik, Universität zu Köln, Zülpicher Straße 77, Köln 50937, GermanyDE

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