Probing equilibrium glass flow up to exapoise viscosities

Area of Science:

• Materials Science
• Condensed Matter Physics
• Physical Chemistry

Background:

• Glasses are out-of-equilibrium systems susceptible to crystallization.
• Studying glass aging is challenging due to extremely long timescales for atomic diffusion in conventional methods.
• The concept of timescale divergence is widely accepted in glass transition theories.

Purpose of the Study:

• To investigate the aging dynamics of glasses on experimentally accessible timescales.
• To challenge the established theories of glass transition and dynamical divergence.
• To explore the relationship between mechanical properties and age in glasses.

Main Methods:

• Rapidly forming glasses using physical vapor deposition (PVD) to achieve various "ages" quickly.
• Isothermally probing the mechanical response (elastic modulus) of these aged glasses.
• Correlating mechanical properties with viscosity and the temperature steepness index.

Main Results:

• A direct correspondence between mechanical response and viscosity was established, even at extremely high viscosity values (up to exapoise).
• A dependence of the elastic modulus on glass age was observed.
• The findings challenge the notion of a dynamical divergence, a key concept in glass transition theories.

Conclusions:

• The study suggests that the conventional understanding of glasses ceasing to flow at a finite temperature might be incorrect.
• Rapidly aged glasses provide a new avenue for studying glass transition phenomena.
• The results necessitate a re-evaluation of current glass transition models, particularly those relying on dynamical divergence.