Metastability, Mode Coupling and the Glass Transition

TL;DR

This paper reformulates mode coupling theory to explain relaxation behaviors in dense fluids without requiring an ideal glass transition temperature, incorporating metastability and defect density coupling.

Contribution

It introduces a fundamental reformulation of MCT that accounts for metastability and removes the need for an ideal glass transition temperature.

Findings

Relaxation sequence can be explained without a $T_0$ transition.

Exponents governing relaxations are weakly temperature-dependent.

Theory aligns with recent experiments showing no evidence of $T_0$.

Abstract

Mode coupling theory (MCT) has been successful in explaining the observed sequence of time relaxations in dense fluids. Previous expositions of this theory showing this sequence have required the existence of an ideal glass transition temperature $T_0$. Recent experiments show no evidence of $T_0$. We show here how the theory can be reformulated, in a fundamental way, such that one retains this sequence of relaxation behaviors but with a smooth temperature dependence and without any indication of $T_0$. The key ingredient in the reformulation is the inclusion of the metastable nature of the glass transition problem through a coupling of the mass density to the defect density. A main result of our theory is that the exponents governing the sequence of time relaxations are weak functions of the temperature in contrast to the results from conventional MCT.