Yunker, Peter J

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2009 - 200912010 - 20113
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  • Publication
    Low-Frequency Vibrations of Soft Colloidal Glasses
    (2010-07-09) Chen, Ke; Ellenbroek, Wouter G; Zhang, Zexin; Yunker, Peter J; Chen, Daniel T.N.; Henkes, Silke; Brito, Carolina; Dauchot, Oliver; Liu, Andrea J; Van Saarloos, Wim; Yodh, Arjun G
    We conduct experiments on two-dimensional packings of colloidal thermosensitive hydrogel particles whose packing fraction can be tuned above the jamming transition by varying the temperature. By measuring displacement correlations between particles, we extract the vibrational properties of a corresponding ‘‘shadow’’ system with the same configuration and interactions, but for which the dynamics of the particles are undamped. The vibrational properties are very similar to those predicted for zerotemperature sphere packings and found in atomic and molecular glasses; there is a boson peak at low frequency that shifts to higher frequency as the system is compressed above the jamming transition.
  • Publication
    Observation of the Disorder-Induced Crystal-to-Glass Transition
    (2010-01-08) Yunker, Peter; Zhang, Zexin; Yodh, Arjun G
    The role of frustration and quenched disorder in driving the transformation of a crystal into a glass is investigated in quasi-two-dimensional binary colloidal suspensions. Frustration is induced by added smaller particles. The crystal-glass transition is measured to differ from the liquid-glass transition in quantitative and qualitative ways. The crystal-glass transition bears structural signatures similar to those of the crystal-fluid transition: at the transition point, the persistence of orientational order decreases sharply from quasilong range to short range, and the orientational order susceptibility exhibits a maximum. The crystal-glass transition also features a sharp variation in particle dynamics: at the transition point, dynamic heterogeneity grows rapidly, and a dynamic correlation length scale increases abruptly.
  • Publication
    Irreversible Rearrangements, Correlated Domains, and Local Structure in Aging Glasses
    (2009-09-09) Yunker, Peter; Zhang, Zexin; Aptowicz, Kevin B.; Yodh, Arjun G.
    Bidisperse colloidal suspensions of temperature-sensitive microgel spheres were quenched from liquid to glass states by a rapid temperature drop, and then the glass was permitted to age. Irreversible rearrangements, events that dramatically change a particle’s local environment, were observed to be closely related to dynamic heterogeneity. The rate of these irreversible events decreased during aging and the the number of particles required to move as part of these irreversible rearrangements increased. Thus, the slowing dynamics of aging were governed by growing, correlated domains of particles. Additionally, short-range order developed, and a spatial decay length scale associated with orientational order was found to grow during aging.
  • Publication