Elastic Constants and Charge Ordering in a'-NaV2O5

TL;DR

This study investigates the temperature-dependent elastic properties of a'-NaV2O5, revealing anomalies and significant shear mode softening linked to charge fluctuations, differing from similar compounds like CuGeO3.

Contribution

It provides new insights into the elastic anomalies and charge ordering in a'-NaV2O5, highlighting the coupling between strain and charge fluctuations.

Findings

Anomalies in elastic constants at Tc for longitudinal modes.

Strong 12% softening of the c66 shear mode.

Charge fluctuation coupling explains shear mode softening.

Abstract

We present the temperature dependence of shear and longitudinal elastic constants in a'-NaV2O5. For the longitudinal c22 and c33 modes we find anomalies at Tc in contrast to the Spin Peierls substance CuGeO3 where only the longitudinal mode along the chain shows a pronounced effect at TSP. The c66 shear mode (propagation along the chain in b-direction polarization in a-direction) shows strong softening of 12%. Such a large effect is absent for all shear modes in CuGeO3. We can interpret this softening with a coupling of the exy symmetry strain to the charge fluctuation of B1g symmetry. We give the possible low temperature charge distribution.