Rung-singlet charge-ordering in alpha'-NaV2O5

TL;DR

This paper proposes a two-band model for alpha'-NaV2O5 that explains simultaneous charge and spin order transitions driven mainly by electron-phonon interactions, with local dimers accounting for the spin gap.

Contribution

It introduces a new two-band model that accounts for the simultaneous charge and spin ordering in alpha'-NaV2O5, contrasting previous zig-zag charge-ordering models.

Findings

The zig-zag charge-ordering model is incompatible with observed transitions.

Electron-phonon interactions primarily drive the charge-spin order transition.

Local dimers explain the weak magnetic effect on the spin gap.

Abstract

We show that the proposed zig--zag charge--ordering model for alpha'--NaV2O5 is incompatible with a single transition that induces both charge--ordering and spin gap. We introduce a two--band model for alpha'--NaV2O5 within which the simultaneous charge--spin order transition is driven principally by electron-phonon interactions. The spin gap is due to the formation of local dimers, thus explaining the weak magnetic effect on this transition.