Monday, 25 June 2007 - 4:40 PM
Clayton 128
103

Light scattering studies of the aging of Laponite glasses and gels

Daniel Bonn, University of Amsterdam and Ecole Normale Superieure, Amsterdam, Netherlands

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 using light scattering 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.