Collective vibrations and soft modes in hard sphere colloid glasses
Frau Dr. Antina Ghosh (FOM Amsterdam (Niederlande))

The glass transition is perhaps one of the important unsolved problem in condensed matter physics. The main question is how to reconcile the liquid-like structure with solid-like mechanical properties. In solids, the structure and mechanics are related directly through the vibrational density of states of the material. Here, we have obtained the density of states of colloidal glasses and supercooled liquids from a normal-mode analysis of particle displacements, measured using confocal microscopy. We find that the spectrum of the vibrations has many ‘soft’, low-frequency modes that are very different in nature from the usual plane waves of crystalline solids. These low frequency soft modes, obtained over short time scales, show strong spatial correlation with the rearrangements that occur over long time scales.