Han Yilong, Shokef Yair, Alsayed Ahmed M, Yunker Peter, Lubensky Tom C, Yodh Arjun G
Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, Pennsylvania 19104, USA.
Nature. 2008 Dec 18;456(7224):898-903. doi: 10.1038/nature07595.
Geometric frustration arises when lattice structure prevents simultaneous minimization of local interaction energies. It leads to highly degenerate ground states and, subsequently, to complex phases of matter, such as water ice, spin ice, and frustrated magnetic materials. Here we report a simple geometrically frustrated system composed of closely packed colloidal spheres confined between parallel walls. Diameter-tunable microgel spheres are self-assembled into a buckled triangular lattice with either up or down displacements, analogous to an antiferromagnetic Ising model on a triangular lattice. Experiment and theory reveal single-particle dynamics governed by in-plane lattice distortions that partially relieve frustration and produce ground states with zigzagging stripes and subextensive entropy, rather than the more random configurations and extensive entropy of the antiferromagnetic Ising model. This tunable soft-matter system provides a means to directly visualize the dynamics of frustration, thermal excitations and defects.
当晶格结构阻碍局部相互作用能同时最小化时，就会出现几何阻挫。它会导致高度简并的基态，并随后产生复杂的物质相，如水冰、自旋冰和阻挫磁性材料。在此，我们报告了一个简单的几何阻挫系统，该系统由紧密堆积在平行壁之间的胶体球组成。直径可调的微凝胶球自组装成具有向上或向下位移的弯曲三角晶格，类似于三角晶格上的反铁磁伊辛模型。实验和理论表明，单粒子动力学受面内晶格畸变支配，这种畸变部分缓解了阻挫，并产生具有锯齿状条纹和次广延熵的基态，而不是反铁磁伊辛模型中更随机的构型和广延熵。这个可调谐的软物质系统提供了一种直接可视化阻挫、热激发和缺陷动力学的方法。
