Renormalization of the spin-Peierls transition due to phonon dynamics
Physikalisches Institut, Universität Bonn -
Nußallee 12, D-53115 Bonn, Germany
Accepted: 30 July 2001
We report results from a systematic strong-coupling expansion of a spin- Heisenberg chain coupled to Einstein phonons and a frustrating next-nearest-neighbor spin interaction. It is not obvious which interaction dominates in the regime of small coupling constants. In the non-adiabatic regime () this model is used to describe the zero-temperature properties of CuGeO3. The linked cluster expansion allows the determination of observables in the thermodynamic limit preserving the full lattice dynamics without a truncation of the phononic Hilbert space. We show that the spin-phonon coupling leads to a renormalization of the elementary triplet dispersion. Surprisingly, in the non-adiabatic regime a substantial renormalization of the spin gap only sets in at much larger couplings than those proposed for CuGeO3. The ground-state magnetic correlations are found to be hardly affected by the spin-phonon coupling, but dominated by the frustrating magnetic interaction in the parameter regime relevant for CuGeO3.
PACS: 63.20.Kr – Phonon-electron and phonon-phonon interactions / 75.10.Jm – Quantized spin models / 75.40.Mg – Numerical simulation studies
© EDP Sciences, 2001