Finite frequency phonon effects in spin-Peierls systems

Using a novel approximation-free quantum Monte Carlo method, we study finite-frequency phonon effects in a spin-1/2 Heisenberg chain with the nearest-neighbor exchange modulated by a bond-local, dispersionless optical phonon. Our results indicate that the dynamic phonons produce important qualitative, as well as quantitative, effects and must be included in order to obtain a proper description of the magnetic properties of spin-Peierls compounds such as GeCuO3 and α′-NaV2O5 both above and below the dimerization temperature.