Coupling between Particle Shape and Long-Range Interaction in the High-Density Regime

We experimentally probe the coupling between particle shape and long-range interaction, using long-range interacting polygons. For two typical space-filling polygons, square and triangle, we find two types of coupling modes that predominantly control the structure formation. Specifically, the rotational ordering of squares brings a lattice deformation that produces a hexagonal-to-rhombic transition in the high density regime, whereas the alignment of triangles introduces a large geometric frustration that causes an order-to-disorder transition. Moreover, the two coupling modes lead to small and large “internal roughness” of the two systems, and thus predominantly control their structure relaxations. Our study thus provides a physical picture to the coupling between long-range interaction effect and short-range shape effect in the high-density regime unexplored before.

我们利用长程相互作用的多边形，对粒子形状与长程相互作用之间的耦合进行了实验探究。对于两种典型的空间填充多边形，正方形和三角形，我们发现了两种主要控制结构形成的耦合模式。具体而言，正方形的旋转有序性导致晶格变形，在高密度区域产生从六边形到菱形的转变，而三角形的排列引入了较大的几何阻挫，导致从有序到无序的转变。此外，这两种耦合模式导致两个系统出现小的和大的“内部粗糙度”，从而主要控制它们的结构弛豫。因此，我们的研究为之前未探索的高密度区域中长程相互作用效应和短程形状效应之间的耦合提供了一个物理图像。