Inherent-State Melting and the Onset of Glassy Dynamics in Two-Dimensional Supercooled Liquids

TL;DR

This paper develops a theory linking the onset temperature of glassy dynamics in 2D supercooled liquids to an inherent-state melting transition driven by dipolar elastic excitations, aligning well with experimental and simulation data.

Contribution

It introduces a microscopic theory for the onset temperature based on inherent-state melting and elastic excitations in two-dimensional supercooled liquids.

Findings

Inherent-state melting transition explains the onset of glassy dynamics.

The melting transition temperature matches observed onset temperatures.

Predictions align with experimental and simulation observations of fluctuations.

Abstract

Below the onset temperature $T_\text{o}$, the equilibrium relaxation time of most glass-forming liquids exhibits glassy dynamics characterized by super-Arrhenius temperature dependence. In this supercooled regime, the relaxation dynamics also proceeds through localized elastic excitations corresponding to hopping events between inherent states, i.e., potential-energy minimizing configurations of the liquid. Despite its importance in distinguishing the supercooled regime from the high-temperature regime, the microscopic origin of $T_\text{o}$ is not yet known. Here, we construct a theory for the onset temperature in two dimensions and find that inherent-state melting transition, described by the binding-unbinding transition of dipolar elastic excitations, delineates the supercooled regime from the high-temperature regime. The corresponding melting transition temperature is in good agreement with the onset temperature found in various two-dimensional atomistic models of glass formers. We discuss the predictions of our theory on the displacement and density correlations of two-dimensional supercooled liquids, which are consistent with observations of the Mermin-Wagner fluctuations in recent experiments and molecular simulations.