Magnon splitting induced by charge ordering in NaV2O5

We consider the effects of charge ordering in NaV2O5 (below T-SP) on the exchange constants and on the magnon dispersion. We show that the experimentally observed splitting of the magnon branches along the a direction is induced by charge ordering. One can distinguish between the proposed "zigzag" and "in-line" patterns of charge ordering. Only the zigzag ordering is consistent with the experimental results regarding (i) the unusual intensity modulation observed in magnetic neutron scattering, (ii) the reduction in the intraladder exchange constant below T-SP, and (iii) the magnon dispersion along a. We estimate the interladder exchange constant to be 1.01 meV 11.7 K for T > T-SP.