Topological Boundary Constraints in Artificial Colloidal Ice

TL;DR

This paper demonstrates through simulations and experiments that boundary engineering in colloidal artificial ice can control bulk behavior, induce rapid ground state formation, and create bistable states or topological strings.

Contribution

It introduces boundary design as a method to manipulate bulk states and topological features in artificial colloidal ice systems, a novel approach in frustrated microstructures.

Findings

Boundaries can rapidly induce the ground state in colloidal ice.

Defects at corners create bistable states and topological strings.

Boundary engineering can be applied to other micro and nanostructures.

Abstract

The effect of boundaries and how these can be used to influence the bulk behaviour in geometrically frustrated systems are both long-standing puzzles, often relegated to secondary role. Here we use numerical simulations and "proof of concept" experiments to demonstrate that boundaries can be engineered to control the bulk behavior in a colloidal artificial ice. We show that an antiferromagnetic frontier forces the system to rapidly reach the ground state (GS), as opposed to the commonly implemented open or periodic boundary conditions. We also show that strategically placing defects at the corners generates novel bistable states, or topological strings which result from competing GS regions in the bulk. Our results could be generalized to other frustrated micro and nanostructures where boundary conditions may be engineered with lithographic techniques.