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Perturbation Theory by Flow Equations: Dimerized and Frustrated S=1/2 Chain

Christian Knetter·Goetz S. Uhrig
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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.

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Christian Knetter, Goetz S. Uhrig. 1999-06-16. Perturbation Theory by Flow Equations: Dimerized and Frustrated S=1/2 Chain. https://doi.org/10.1007/s100510050026

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