Strain pattern in supercooled liquids

TL;DR

This paper investigates strain correlations in supercooled liquids near the glass transition, revealing persistent elastic-like strain patterns that follow a scaling law, even beyond the structural relaxation time.

Contribution

It introduces a mode-coupling theory for strain fluctuations and combines it with experimental and simulation data to explain long-range strain signatures near the glass transition.

Findings

Eshelby-strain pattern persists at long times and high viscosities

Strain signatures follow a universal scaling law near the glass transition

Elastic-like strain correlations are observed even after shear modulus relaxation

Abstract

Investigations of strain correlations at the glass transition reveal unexpected phenomena. The shear strain fluctuations show an Eshelby-strain pattern ($\,\sim \cos{(4\theta)}/r^2\,$), characteristic for elastic response, even in liquids at long times [1]. We address this using a mode-coupling theory for the strain fluctuations in supercooled liquids and data from both, video microscopy of a two-dimensional colloidal glass former and simulations of Brownian hard disks. We show that long-ranged and long-lived strain-signatures follow a scaling law valid close to the glass transition. For large enough viscosities, the Eshelby-strain pattern is visible even on time scales longer than the structural relaxation time $\tau$ and after the shear modulus has relaxed to zero.