Fifth-order susceptibility unveils growth of thermodynamic amorphous order in glass-formers

TL;DR

This study uses high-precision nonlinear dielectric experiments to demonstrate that the growth of thermodynamic amorphous order underpins the glass transition, revealing compact domains and supporting a thermodynamic phase transition perspective.

Contribution

The paper provides experimental evidence using third- and fifth-order susceptibilities to support the thermodynamic phase transition theory of glass formation, highlighting the nature of growing amorphous domains.

Findings

Strong support for thermodynamic amorphous order theories

Growing transient domains are compact with fractal dimension d_f=3

Glass transition may be a critical phenomenon different from second-order phase transitions

Abstract

Glasses are ubiquitous in daily life and technology. However the microscopic mechanisms generating this state of matter remain subject to debate: Glasses are considered either as merely hyper-viscous liquids or as resulting from a genuine thermodynamic phase transition towards a rigid state. We show that third- and fifth-order susceptibilities provide a definite answer to this longstanding controversy. Performing the corresponding high-precision nonlinear dielectric experiments for supercooled glycerol and propylene carbonate, we find strong support for theories based upon thermodynamic amorphous order. Moreover, when lowering temperature, we find that the growing transient domains are compact - that is their fractal dimension d_f = 3. The glass transition may thus represent a class of critical phenomena different from canonical second-order phase transitions for which d_f < 3.