A new view of the electronic structure of the spin-Peierls compound -NaVO

Abstract:

The present understanding of the electronic and magnetic properties of -NaV₂O₅ is based on the hypothesis of strong charge disproportionation into V⁴⁺ and V⁵⁺, which is assumed to lead to a spin-1/2 Heisenberg chain system. A recent structure analysis shows, however, that the V-ions are in a mixed valence state and indistiguishable. We propose an explanation for the insulating state, which is not based on charge modulation, and show that strong correlations together with the Heitler-London character of the relevant intermediate states naturally lead to antiferromagnetic Heisenberg chains. The interchain coupling is weak and frustrated, and its effect on the uniform susceptibility is found to be small.