Research at FAST

Department of Applied Physics Department of Applied Physics 122 Qualification BSc (HKU) PhD (UMich) Postdoc (Yale) ORCID ID 0000-0002-0476-1857 Representative Publications • Physical Review Letters 124, 2020 , 095501 • Journal of Statistical Mechanics: Theory and Experiment, 2019 , 094014 • Physical Review E 99, 2019 , 010501 • Physical Review B 95, 2017 , 184202 • Macromolecules 48, 2015 , 5034 • Journal of Materials Chemistry C 3, 2015 , 12457 • Science 343, 2014 , 975 • Science 328, 2010 , 1676 • Physical Review Letters 95, 2005 , 086102 • Physical Review Letters 89, 2002 , 216102 Dr LAM Chi Hang Associate Professor Research Overview Many liquids can be quenched into the glassy states when super-cooled rapidly. We study the fundamental nature of the glass transition focusing on a dynamic facilitation behavior in which defects in the form of voids aid the motions of each other. Techniques including molecular dynamics simulations, lattice model simulations, random-tree theoretical analysis, and colloidal fluid experiments are employed. Using our theoretical models, we have recently explained an aging phenomenon of glassy polymer known as Kovacs’ expansion gap paradox, which describes the dependence of the energy relaxation rate on the initial temperature of a heated polymer sample even close to equilibrium. We find that the system relaxes by nucleation and expansion of warmer mobile domains having attained the final temperature, against cooler immobile domains maintained at the initial temperature. A small population of these cooler regions persists close to equilibrium, thus explaining the paradox. Results are published in Physical Review Letters.