Free energy of sheared colloidal glasses

TL;DR

This paper introduces a free energy framework for sheared colloidal glasses, revealing how non-affine displacements and dissipation influence their response to stress, with direct measurements and a mean-field theoretical model.

Contribution

It presents the first direct measurement of free energy in strained colloidal glasses and a mean-field model that separates affine and nonaffine displacement effects.

Findings

Nonaffine displacements increase with shear due to structural loss.

Free energy decreases under shear, contrasting crystalline behavior.

Mean-field theory successfully relates free energy to displacements.

Abstract

We develop a free energy framework to describe the response of glasses to applied stress. Unlike crystals, for which the free energy increases quadratically with strain due to affine displacements, for glasses, the nonequilibrium free energy decreases due to complex interplay of non-affine displacements and dissipation. We measure this free energy directly in strained colloidal glasses, and use mean-field theory to relate it to affine and nonaffine displacements. Nonaffine displacements grow with applied shear due to shear-induced loss of structural connectivity. Our mean-field model allows for the first time to disentangle the complex contributions of affine and nonaffine displacements and dissipation in the transient deformation of glasses.