The Spin-SAF transition in NaV2O5 induced by spin-pseudospin coupling

We present microscopic estimates for the spin-spin and spin-speudospin interactions of the quarter-filled ladder compound NaV2O5, obtained by exactly diagonalizing appropriate clusters of the underlying generalized Hubbard Hamiltonian. We present evidence for a substantial interladder spin-pseudospin interaction term which would allow simultaneously for the superantiferroelectric (SAF) charge (pseudospin) ordering and spin dimerization. We discuss the values of the coupling constants appropriate for NaV2O5 and deduce the absence of a soft antiferroelectric mode

On the Stacking Charge Order in NaV2O5

We propose a mechanism for the observed stacking charge order in the quarter-filled ladder compound NaV2O5. Via a standard mapping of the charge degrees of freedom onto Ising spins we explain the stacking order as a result of competition between couplings of the nearest and next-nearest planes with the 4-fold degenerate super-antiferroelectric in-plane order.Comment: 4 pages, 5 figure