Lattice softening effects at the Mott critical point of Cr-doped V$_2$O$_3$

TL;DR

This study investigates lattice softening near the Mott critical point in Cr-doped V2O3 through sound velocity measurements, revealing a scalar transition consistent with DMFT but with smaller effects than theoretical predictions.

Contribution

It provides experimental evidence of lattice softening at the Mott transition and compares results with DMFT predictions, highlighting discrepancies in effect magnitude.

Findings

Large dip in $c_{33}$ near critical point

No critical signs in shear modulus $c_{44}$

Effect size smaller than DMFT predictions

Abstract

We have performed sound velocity measurements in (V$_{1-x}$Cr$_x$)$_2$O$_3$ in the vicinity of the critical point of the first order Mott transition line. The pressure sweeps at constant temperature reveal a large dip in the $c_{33}$ compression modulus, this dip sharpens as the critical point is approached. We do not observe signs of criticality on the shear modulus $c_{44}$ which is consistent with a transition governed by a scalar order parameter, in accordance with the DMFT description of the transition. However, the amplitude of the effect is an order of magnitude smaller than the one obtained from DMFT calculations for a single band Hubbard model. We analyze our results using a simple model with the electronic response function obtained from the scaling relations for the conductivity.