Effective charge and spin Hamiltonian for the quarter-filled ladder compound a'-NaV2O5
Fachbereich Physik, University of the Saarland, 66041 Saarbrücken, Germany
Corresponding author: a firstname.lastname@example.org
Revised: 30 August 2000
Published online: 15 December 2000
An effective intra- and inter-ladder charge-spin Hamiltonian for the quarter-filled ladder compound a'-NaV2O5 has been derived by using the standard canonical transformation method. In the derivation, it is clear that a finite inter-site Coulomb repulsion is needed to get a meaningful result otherwise the perturbation becomes ill-defined. Various limiting cases depending on the values of the model parameters have been analyzed in detail and the effective exchange couplings are estimated. We find that the effective intra-ladder exchange may become ferromagnetic for the case of zig-zag charge ordering in a purely electronic model. We estimate the magnitude of the effective inter-rung Coulomb repulsion in a ladder and find it to be about one-order of magnitude too small in order to stabilize charge-ordering.
PACS: 71.10.Fd – Lattice fermion models (Hubbard model, etc.) / 75.30.Et – Exchange and superexchange interactions / 64.60.-i – General studies of phase transitions
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000