Regensburg 2016 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 36: Complex Fluids and Colloids V (joint session DY/BP/CPP)

DY 36.8: Vortrag

Mittwoch, 9. März 2016, 12:00–12:15, H47

Defect-mediated melting of two-dimensional colloidal quasicrystals — Miriam Martinsons and •Michael Schmiedeberg — Institut für Theoretische Physik 1, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058 Erlangen, Germany

Quasicrystals are structures that possess long range order but no translational symmetry. Due to additional degrees of freedom in quasicrystals there are properties and phenomena that for quasicrystalline structures significantly differ from their counterpart in periodic crystals.

We study how thermally excited excitations or defects develop in two-dimensional colloidal quasicrystals close to the melting transition. According to an extension of the KTHNY theory [1], the formation and dissociation of pairs of dislocation and disclinations is expected to cause the melting of the quasicrystal. Melting should occur via an intermediate phase termed pentahedratic phase [1].

We use Monte-Carlo and Brownian dynamics simulations to study the melting process of decagonal colloidal quasicrystals. By analyzing the positional and bond-orientational correlation functions during the melting process we reveal an intermediate state with quasi-long ranged orientational order but only short ranged positional order as in the predicted pentahedratic phase. Furthermore, we observe network-like structures composed of defects spanning through defect-free areas as well as a coexistence between the intermediate phase and the fluid.

[1] P. De, R.A. Pelcovits, J. Phys. A 22, 1167 (1989); Phys. Rev. B 38, 5042 (1988).