A new view of the electronic structure of the spin-Peierls compound alpha'-NaV2O5

TL;DR

This paper challenges the traditional charge disproportionation model of alpha'-NaV2O5, proposing instead that strong electron correlations and the Heitler-London mechanism explain its insulating and magnetic properties without charge modulation.

Contribution

It introduces a new explanation for the electronic structure of alpha'-NaV2O5 based on correlations and intermediate states, diverging from the charge disproportionation hypothesis.

Findings

V-ions are in a mixed valence state, not charge disproportionated.

Strong correlations and Heitler-London states lead to antiferromagnetic chains.

Interchain coupling is weak and has minimal impact on susceptibility.

Abstract

The present understanding of the electronic and magnetic properties of $\alpha'$-NaV$_2$O$_5$ is based on the hypothesis of strong charge disproportionation into V$^{4+}$ and V$^{5+}$, 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.