  
|
    
|
The European Physical Journal B
ISSN: 1434-6028 (printed version)
ISSN: 1434-6036 (electronic version)
Abstract Volume 1 Issue 1 (1998) pp 19-28
Dynamical properties of low-dimensional $\mathsf{CuGeO_3}$ and $\mathsf{NaV_2O_5}$ spin-Peierls systems
D. Augier, D. Poilblanc (a)
Laboratoire de Physique Quantique et Unité Mixte de Recherche CNRS 5626, Université Paul Sabatier, 31062 Toulouse, France
Received: 30 July 1997 / Revised: 16 September 1997 / Accepted: 10 October 1997
Abstract: Properties of low-dimensional spin-Peierls systems are described by using a one-dimensional S=1/2 antiferromagnetic Heisenberg chain linearly coupled to a single phonon mode of wave vector $\pi$ (whose contribution is expected to be dominant). By exact diagonalizations of small rings with up to 24 sites supplemented by a finite size scaling analysis, static and dynamical properties are investigated. Numerical evidences are given for a spontaneous discrete symmetry breaking towards a spin gapped phase with a frozen lattice dimerization. Special emphasis is put on the comparative study of the two inorganic spin-Peierls compounds CuGeO3 and NaV2O5 and the model parameters are determined from a fit of the experimental spin gaps. We predict that the spin-phonon coupling is 2 or 3 times larger in NaV2O5 than in CuGeO3. Inelastic neutron scattering spectra are calculated and similar results are found in the single phonon mode approximation and in the model including a static dimerization. In particular, the magnon S=1 branch is clearly separated from the continuum of triplet excitations by a finite gap.
PACS. 64.70.Kb Solid-solid transitions - 71.27.+a Strongly correlated electron systems; heavy fermions - 75.10.Jm Quantized spin models
(a) e-mail: didier@irsamc2.ups-tlse.fr
Online publication: February 4, 1998
helpdesk@link.springer.de
© EDP Sciences, Springer-Verlag 1998