Effective spin models for spin-phonon chains by flow equations

  • C. Raas
  • A. Bühler
  • G.S. Uhrig
  • 92 Downloads

Abstract:

We investigate the anti-adiabatic limit of an anti-ferromagnetic S = 1/2 Heisenberg chain coupled to Einstein phonons. The flow equation method is used to decouple the spin and the phonon part of the Hamiltonian. In the effective spin model long range spin-spin interactions are generated. We determine the phase transition from a gapless state to a gapped (dimerized) phase, which occurs at a non-zero value of the spin-phonon coupling. In the effective phonon sector a phonon hardening is observed.

PACS. 75.10.Jm Quantized spin models – 63.20.Kr Phonon-electron and phonon-phonon interactions – 63.20.Ls Phonon interactions with other quasiparticles 

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Copyright information

© EDP Sciences, Springer-Verlag 2001

Authors and Affiliations

  • C. Raas
    • 1
  • A. Bühler
    • 1
  • G.S. Uhrig
    • 1
  1. 1.Institut für Theoretische Physik, Universität zu Köln, Zülpicher Str. 77, 50937 Köln, GermanyDE

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