Geometric Frustration in Buckled Colloidal Monolayers

TL;DR

This study introduces a colloidal system that exhibits geometric frustration similar to magnetic models, allowing direct visualization of frustration dynamics, ground states, and defect behavior in a tunable soft matter setup.

Contribution

It demonstrates a simple colloidal system that models geometric frustration, revealing new ground states and dynamics distinct from traditional magnetic systems.

Findings

Colloidal spheres form a buckled triangular lattice with antiferromagnetic-like order.

In-plane distortions partially relieve frustration, leading to zigzag stripe ground states.

The system allows direct observation of frustration, excitations, and defects in real time.

Abstract

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.