2008/07/24 by Yilong Han, Yair Shokef, Ahmed AlSayed +6 · 5 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Condensed matter physics #Degenerate energy levels #Frustration #Geometrical frustration #Hard spheres #Hexagonal lattice #Ising model #Material Dynamics and Properties #Materials science #Physics #Quantum mechanics #SPHERES #Spin ice #Theoretical and Computational Physics #Thermal fluctuations #cond-mat.soft #cond-mat.stat-mech
paper · pdf · doi:10.1038/nature07595
published as Nature 456, 898 (2008) · (*) These authors contributed equally to this work. Main Text: 6 pages, 5 figures. Supplementary Information and Online Movies available at http://www.physics.upenn.edu/~yair/frustration.html
arxiv created 2008/07/24 · openalex publication_date 2008/12/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Geometric frustration arises when lattice structure prevents simultaneous minimization of local interactions. It leads to highly degenerate ground states and, subsequently, 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 an uncharted arena in which the dynamics of frustration, thermal excitations and defects can be directly visualized.