Experimental observation of the intricate free-energy landscape for a soft glassy system

TL;DR

This paper experimentally investigates the complex free-energy landscape of colloidal glassy systems, revealing multiple pathways and states, including gels and glasses, and demonstrating the intricate dynamics involved in aging and state transitions.

Contribution

It provides experimental evidence for multiple pathways in the free energy landscape of colloidal glasses, distinguishing gel and glass states and showing complex aging dynamics.

Findings

Multiple paths lead to different non-ergodic states.

Gel and glass states are global minima in the same landscape.

Transitions can occur in either direction with hesitations.

Abstract

In the free energy landscape picture of glassy systems, the slow dynamics characteristic of these systems is believed to be due to the existence of a complicated free-energy landscape with many local minima. We show here that for a colloidal glassy material multiple paths can be taken through the free energy landscape, that can even lead to different 'final' non-ergodic states at the late stages of aging. We provide clear experimental evidence for the distinction of gel and glassy states in the system and show that for a range of colloid concentrations, the transition to non-ergodicity can occur in either direction (gel or glass), and may be accompanied by 'hesitations' between the two directions. This shows that colloidal gels and glasses are merely global free-energy minima in the same free energy landscape, and that the paths leading to these minima can indeed be complicated.