Dynamic facilitation explains democratic particle motion of metabasin transitions

TL;DR

This paper demonstrates that the seemingly homogeneous particle rearrangements during metabasin transitions in supercooled liquids are actually driven by localized facilitation, revealing the underlying heterogeneity of the process.

Contribution

It shows that democratic particle motion during metabasin transitions results from dynamic facilitation, linking microscopic facilitation events to macroscopic transition behavior.

Findings

Metabasin transitions involve sequences of local facilitation events.

Observed homogeneous motion is due to small spatial window analysis.

Transitions are fundamentally heterogeneous despite appearing homogeneous.

Abstract

Transitions between metabasins in supercooled liquids seem to occur through rapid "democratic" collective particle rearrangements. Here we show that this apparent homogeneous particle motion is a direct consequence of dynamic facilitation. We do so by studying metabasin transitions in facilitated spin models and constrained lattice gases. We find that metabasin transitions occur through a sequence of locally facilitated events taking place over a relatively short time frame. When observed on small enough spatial windows these events appear sudden and homogeneous. Our results indicate that metabasin transitions are essentially "non-democratic" in origin and yet another manifestation of dynamical heterogeneity in glass formers.