https://doi.org/10.1007/s100510050148
Dynamical properties of low-dimensional CuGeO3 and NaV205 spin-Peierls systems
Laboratoire de Physique Quantique et Unité Mixte de Recherche
CNRS 5626,
Université Paul Sabatier, 31062 Toulouse, France
Corresponding author: a didier@irsamc2.ups-tlse.fr
Received:
30
July
1997
Revised:
16
September
1997
Accepted:
10
October
1997
Published online: 15 January 1998
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 π (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
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1998