title: Fractionalization of interstitials in curved colloidal crystals.
abstract: Understanding the effect of curvature and topological frustration in crystals yields insights into the fragility of the ordered state. For instance, a one-dimensional crystal of identical charged particles can accommodate an extra particle (interstitial) if all the particle positions are readjusted, yet in a planar hexagonal crystal interstitials remain trapped between lattice sites and diffuse by hopping. Using optical tweezers operated independently of three-dimensional imaging, we inserted interstitials in a lattice of similar colloidal particles sitting on flat or curved oil/glycerol interfaces, and imaged the ensuing dynamics. We find that, unlike in flat space, the curved crystals self-heal through a collective particle rearrangement that redistributes the increased density associated with the interstitial. This process can be interpreted in terms of the out-of-equilibrium interaction of topological defects with each other and with the underlying curvature. Our observations suggest the existence of particle fractionalization on curved surface crystals.
authors.affiliation: James Franck Institute, University of Chicago, 929 E 57th street, Chicago, Illinois 60637, USA. wtmirvine@uchicago.edu
authors.forename: William T M
authors.initials: WT
authors.lastname: Irvine
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Bowick
authors.forename: Paul M
authors.initials: PM
authors.lastname: Chaikin