Charge Ordering and Spin gap in NaV_2O_5

TL;DR

This paper proposes a new ground state for NaV_2O_5, where intersite Coulomb interactions cause charge ordering and a spin gap, differing from the previously assumed spin-Peierls state, aligning with experimental observations.

Contribution

It introduces a novel charge-ordered state induced by intersite Coulomb interactions in NaV_2O_5, challenging the conventional spin-Peierls interpretation.

Findings

Charge ordering along V-ion ladders due to intersite Coulomb interaction

Formation of a spin gap from localized spins between ladders

Consistency with existing experimental data

Abstract

A possible ground state of NaV_2O_5 is proposed based on the Hartree approximation for both on-site and intersite Coulomb interactions. The results indicate that the intersite Coulomb interaction induces a zigzag type of charge disproportionation (i.e. charge ordering) along the ladders of V-ions resulting in the localized spins between neighboring ladders to form a spin gap. This new state, which is different from the spin-Peierls state so far believed, seems to be consistent with the existing experimental results.