Self-consistent variational approach to the Peierls and the spin-Peierls transition
Abstract
We consider a one dimensional XXZ spin chain (or equivalently a half filled band of spinless fermions) interacting with phonons of frequency ω_0. By gaussian integration over the phonons, we derive a non-local bosonized action describing this system at T=0. Using a variational ansatz, we study the behavior of the gap of the system as a function of the frequency ω0 and the spin-phonon coupling. We find that the spin-Peierls gap is described for small ω0 by the Cross and Fisher(Phys. Rev. B 19), 402 (1979) mean-field theory (adiabatic regime), and for large ω0 by a sine-Gordon theory (antiadiabatic regime). The variational approach allows a description of the smooth crossover between the two regimes. This approach is compared with the renormalization group approach.
- Publication:
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APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARJ25013O