准周期光场作用下胶体单分子膜中反常对称性的扩散
Proliferation of anomalous symmetries in colloidal monolayers subjected to quasiperiodic light fields
摘要：
准晶提供了一类具有迷人性质的材料。尽管准晶在许多技术应用上有很大的潜力，但人们对准晶形成的条件仍然知之甚少。目前，还不清楚为什么大多数准晶具有5或10重对称性，但从未观察到具有7或9重对称性的单一例子。在这里，我们报告的几何约束，阻碍形成的准晶体与某些对称性的胶体模型系统。在实验上，胶体准晶是通过使微米大小的颗粒经受由n=5或7个激光束产生的二维准周期势场来产生的。我们的结果清楚地表明，准晶顺序是更容易建立n = 5相比，n = 7。随着激光强度的增加，我们观察到的胶体首先采用准周期秩序在局部地区，然后横向生长，直到扩展的准晶层的形式。作为准周期性起源的成核位点，我们在激光图案中识别出高度对称的图案。我们发现，它们的密度强烈地随n而变化，并且令人惊讶的是，对于那些在原子系统中从未观察到的准晶对称性，它们的密度恰好是最小的。由于这种高对称性基序也存在于原子准晶中，它们在其中充当优先吸附位点，这表明确实是这种基序的缺陷导致了具有例如7重对称性的材料的缺乏。
英文摘要：
Quasicrystals provide a fascinating class of materials with intriguing properties. Despite a strong potential for numerous technical applications, the conditions under which quasicrystals form are still poorly understood. Currently, it is not clear why most quasicrystals hold 5- or 10-fold symmetry but no single example with 7 or 9-fold symmetry has ever been observed. Here we report on geometrical constraints which impede the formation of quasicrystals with certain symmetries in a colloidal model system. Experimentally, colloidal quasicrystals are created by subjecting micron-sized particles to two-dimensional quasiperiodic potential landscapes created by n=5 or seven laser beams. Our results clearly demonstrate that quasicrystalline order is much easier established for n = 5 compared to n = 7. With increasing laser intensity we observe that the colloids first adopt quasiperiodic order at local areas which then laterally grow until an extended quasicrystalline layer forms. As nucleation sites where quasiperiodicity originates, we identify highly symmetric motifs in the laser pattern. We find that their density strongly varies with n and surprisingly is smallest exactly for those quasicrystalline symmetries which have never been observed in atomic systems. Since such high symmetry motifs also exist in atomic quasicrystals where they act as preferential adsorption sites, this suggests that it is indeed the deficiency of such motifs which accounts for the absence of materials with e.g. 7-fold symmetry.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
