Mott metal-insulator transition on compressible lattices

TL;DR

This paper studies how coupling between electronic Mott transitions and lattice elasticity alters critical behavior, predicting a mean-field elasticity breakdown near the Mott endpoint in certain materials.

Contribution

It reveals that lattice elasticity preempts Ising criticality at the Mott endpoint, leading to a Landau criticality with nonlinear elasticity behavior.

Findings

Elasticity dominates near the Mott endpoint within 8% temperature range.

Hooke's law breaks down with a mean-field exponent.

Critical elasticity influences the phase transition in kappa-(BEDT-TTF)2X.

Abstract

The critical properties of the finite temperature Mott endpoint are drastically altered by a coupling to crystal elasticity, i.e., whenever it is amenable to pressure tuning. Similar as for critical piezoelectric ferroelectrics, the Ising criticality of the electronic system is preempted by an isostructural instability, and long-range shear forces suppress microscopic fluctuations. As a result, the endpoint is governed by Landau criticality. Its hallmark is thus a breakdown of Hooke's law of elasticity with a non-linear strain-stress relation characterized by a mean-field exponent. Based on a quantitative estimate, we predict critical elasticity to dominate the temperature range DeltaT/Tc ~ 8% close to the Mott endpoint of kappa-(BEDT-TTF)2X.