Probing equilibrium glass flow up to exapoise viscosities

TL;DR

This study uses vapor-deposited glasses with varying ages to investigate their flow behavior at extremely high viscosities, challenging the idea of a finite-temperature flow cessation in glasses.

Contribution

It introduces a method to probe glass flow up to exapoise viscosities using vapor-deposited glasses, questioning the divergence of viscosity at the glass transition.

Findings

Elastic modulus depends on glass age

Viscosity does not diverge at finite temperature

Challenges traditional glass transition theories

Abstract

Glasses are out-of-equilibrium systems aging under the crystallization threat. During ordinary glass formation, the atomic diffusion slows down rendering its experimental investigation impractically long, to the extent that a timescale divergence is taken for granted by many. We circumvent here these limitations, taking advantage of a wide family of glasses rapidly obtained by physical vapor deposition directly into the solid state, endowed with different "ages" rivaling those reached by standard cooling and waiting for millennia. Isothermally probing the mechanical response of each of these glasses, we infer a correspondence with viscosity along the equilibrium line, up to exapoise values. We find a dependence of the elastic modulus on the glass age, which, traced back to temperature steepness index of the viscosity, tears down one of the cornerstones of several glass transition theories: the dynamical divergence. Critically, our results suggest that the conventional wisdom picture of a glass ceasing to flow at finite temperature could be wrong.