The race to the bottom: approaching the ideal glass?

TL;DR

This paper reviews recent experimental and theoretical advances in understanding the glass transition, focusing on whether an ideal thermodynamic glass state exists, by approaching the putative transition closely.

Contribution

It synthesizes new techniques and findings that aim to resolve the debate over the thermodynamic versus dynamic nature of the glass transition.

Findings

Emerging consensus on approaching the thermodynamic transition

New techniques provide insights into the existence of an ideal glass

Implications for the fundamental understanding of glass formation

Abstract

Key to resolving the scientific challenge of the glass transition is to understand the origin of the massive increase in viscosity of liquids cooled below their melting temperature (avoiding crystallisation). A number of competing and often mutually exclusive theoretical approaches have been advanced to describe this phenomenon. Some posit a bona fide thermodynamic phase to an "ideal glass", an amorphous state with exceptionally low entropy. Other approaches are built around the concept of the glass transition as a primarily dynamic phenomenon. These fundamentally different interpretations give equally good descriptions of the data available, so it is hard to determine which -- if any -- is correct. Recently however this situation has begun to change. A consensus has emerged that one powerful means to resolve this longstanding question is to approach the putative thermodynamic transition sufficiently closely, and a number of techniques have emerged to meet this challenge. Here we review the results of some of these new techniques and discuss the implications for the existence -- or otherwise -- of the thermodynamic transition to an ideal glass.