A Dramatically Growing Shear Rigidity Length Scale in a Supercooled Glass Former ($NiZr_2$)

TL;DR

This paper identifies and demonstrates a growing shear rigidity length scale in supercooled liquids approaching the glass transition, using molecular dynamics simulations of NiZr2, which may be experimentally verifiable.

Contribution

It introduces a new length scale related to shear penetration depth that grows significantly near the glass transition, supported by simulation evidence.

Findings

Shear penetration depth increases by at least an order of magnitude near the glass transition.

The length scale exhibits Ising-like scaling behavior.

Growth of the length scale correlates with viscosity increase and Stokes-Einstein breakdown.

Abstract

Finding a suitably growing length scale that increases in tandem with the immense viscous slowdown of supercooled liquids is an open problem associated with the glass transition. Here, we define and demonstrate the existence of one such length scale which may be experimentally verifiable. This is the length scale over which external shear perturbations appreciably penetrate into a liquid as the glass transition is approached. We provide simulation based evidence of its existence, and its growth by at least an order of magnitude, by using molecular dynamics simulations of NiZr2, a good fragile glass former. On the probed timescale, upon approaching the glass transition temperature from above, this length scale, {\xi} is also shown to be consistent with Ising-like scaling. Furthermore, we demonstrate the possible scaling of {\xi} about the temperature at which super-Arrhenius growth of viscosity, and a marked growth of the penetration depth sets in. Our simulation results suggest that upon supercooling, marked initial increase of the shear penetration depth in fluids may occur in tandem with the breakdown of the Stokes-Einstein relation.