Electron-phonon and spin-phonon coupling in NaV$_{2}$O$_{5}$: charge fluctuations effect

TL;DR

This paper investigates how the asymmetric crystal environment in NaV$_{2}$O$_{5}$ causes strong electron-phonon and spin-phonon interactions, leading to charge ordering and modulated magnetic interactions at low temperatures.

Contribution

It reveals the role of charge fluctuations induced by lattice asymmetry in driving charge order and spin-phonon coupling in NaV$_{2}$O$_{5}$.

Findings

Charge fluctuations promote charge ordering at low temperatures.

Charge fluctuations modulate spin-spin superexchange interactions.

Strong spin-phonon coupling observed in the low-temperature phase.

Abstract

We show that the asymmetric crystal environment of the V site in the ladder compound NaV$_{2}$O$_{5}$ leads to a strong coupling of vanadium 3d electrons to phonons. This coupling causes fluctuations of the charge on the V ions, and favors a transition to a charge-ordered state at low temperatures. In the low temperature phase the charge fluctuations modulate the spin-spin superexchange interaction, resulting in a strong spin-phonon coupling.