Particle dynamics in supercooled liquids are often dominated by stringlike motions in which lines of particles perform activated hops cooperatively. The structural features triggering these motions, crucial in understanding glassy dynamics, remain highly controversial. We experimentally study microscopic particle dynamics in colloidal glass formers at high packing fractions. With a small polydispersity leading to glass-crystal coexistence, a void in the form of a vacancy in the crystal can diffuse reversibly into the glass and further induces stringlike motions. In the glass, a void takes the form of a quasivoid consisting of a few neighboring free volumes and is transported by the stringlike motions it induces. In fully glassy systems with a large polydispersity, similar quasivoid actions are observed. The mobile particles cluster into stringlike or compact geometries, but the compact ones can be further broken down into connected sequences of strings, establishing their general importance. Furthermore, we can also create quasivoids and trigger stringlike motions using a local external field in a highly controllable manner.
Prof. Yip is currently a professor in the Faculty of Science at Harbin Institute of Technology (Shenzhen) (HITSZ). His research expertise are the physics of glass transition and nanomaterials. He received his bachelor’s degree and PhD degree from the University of Hong Kong. Prior to joining the HITSZ, he worked as a Research Associate and Instructor at the Hong Kong Polytechnic University.