Influence of an amorphous wall on the distribution of localized excitations in a colloidal glass-forming liquid

TL;DR

This study investigates how an amorphous wall influences localized excitations in a colloidal glass-forming liquid, revealing complex spatial profiles and proposing a method to evaluate dynamical facilitation's role in structural relaxation.

Contribution

It introduces an analysis of excitation distributions near an amorphous wall, connecting dynamical facilitation with RFOT theory, and compares new length scales with existing ones.

Findings

Spatial excitation profiles show non-monotonicity and oscillations.

A new length scale $\xi_c$ is extracted and compared with $\xi_{dyn}$.

Results suggest a method to evaluate dynamical facilitation in glassy liquids.

Abstract

Elucidating the nature of the glass transition has been the holy grail of condensed matter physics and statistical mechanics for several decades. A phenomenological aspect that makes glass formation a conceptually formidable problem is that structural and dynamic correlations in glass-forming liquids are too subtle to be captured at the level of conventional two-point functions. As a consequence, a host of theoretical techniques, such as quenched amorphous configurations of particles, have been devised and employed in simulations and colloid experiments to gain insights into the mechanisms responsible for these elusive correlations. Very often, though, the analysis of spatio-temporal correlations is performed in the context of a single theoretical framework, and critical comparisons of microscopic predictions of competing theories are thereby lacking. Here, we address this issue by analysing the distribution of localized excitations, which are building blocks of relaxation as per the Dynamical Facilitation (DF) theory, in the presence of an amorphous wall, a construct motivated by the Random First-Order Transition theory (RFOT). We observe that spatial profiles of the concentration of excitations exhibit complex features such as non-monotonicity and oscillations. Moreover, the smoothly varying part of the concentration profile yields a length scale $\xi_c$, which we compare with a previously computed length scale $\xi_{dyn}$. Our results suggest a method to assess the role of dynamical facilitation in governing structural relaxation in glass-forming liquids.