Title: 2D and 3D colloidal glass transitions: Does dimensionality really matter?
Speaker: Prof. Eric Weeks
Institute: Emory University
Location: ABB 102
Phase transitions significantly differ between two-dimensional and three-dimensional systems, but the influence of dimensionality on the glass transition is unresolved. Colloids are a useful model of the glass transition: these samples are composed of micron-sized particles in a liquid, and the particles diffuse due to Brownian motion. At sufficiently high concentration, the particle diffusion is negligible and the sample is considered glassy. We use microscopy to study colloidal systems as they approach their glass transitions at high concentrations, and find differences between 2D and 3D. We find that in 2D particles can undergo large displacements without changing their position relative to their neighbors, in contrast with 3D. This is related to Mermin-Wagner long-wavelength fluctuations that influence phase transitions in 2D. However, when measuring particle motion only relative to their neighbors, 2D and 3D have similar behavior as the glass transition is approached, showing that the long wavelength fluctuations do not cause a fundamental distinction between 2D and 3D glass transitions.