Quasicrystals are structures with long-range positional and orientational
order. However, they cannot be periodic since they possess
rotational symmetries such as 5- or 10-fold axis that are forbidden
for conventional crystals. These structures lead to new and unique
features of matter. Therefore, a lot of effort has recently been initiated
to grow atomic quasicrystals on quasicrystalline surfaces.
To mimic this situation, 2D light-interference patterns have been used to
study the phase behavior of micron-sized colloidal particles in a 2D
quasicrystalline potential and new ordered phases have been identified
[1,2].
This talk reviews our recent work on how charge-stabilized colloidal
particles order on a substrate with decagonal symmetry using Monte-Carlo
simulations [2]. We report phasediagrams as a function of particle density
and strength of substrate potential and identify quasicrystalline phases
with 10- and also pure 20-fold bond-orientational order but also a
modified version of an Archimedean tiling. We demonstrate that
so-called phasonic displacements help to grow domains of these
Archimedean-like tilings [3].
Finally, we present first results on how hard needles realized by
nanorods, such as organic molecules, or needle-shaped colloidal rods
order in a decagonal potential. For small substrate strength $V_0$, we
still observe a well established nematic order that decreases with
increasing $V_0$ when the hard needles cluster together in domains
oriented along the five equivalent directions of the substrate potential.
[1] J. Mikhael et al., Nature (London) 454, 501 (2008).
[2] M. Schmiedeberg and H. Stark, Phys. Rev. Lett. 101, 218302 (2008).
[3] M. Schmiedeberg et al., to be published in Eur. Phys. J. E.