Ice Rule and Emergent Frustration in Particle Ice

In this talk I will describe recent experimental results obtained by using artificial particle ice systems, namely interacting paramagnetic colloids gravitationally trapped within lithographic structures. With experiments, theory and simulations, I will demonstrate that in mixed coordination geometries, entropy-driven negative monopoles spontaneously appear at a density determined by the vertex-mixture ratio. Unlike its spin-based analogue, the colloidal system displays a “fragile ice” manifold, where local energetics oppose the ice rule, which is instead enforced through conservation of the global topological charge. The fragile colloidal ice, stabilized by topology, can be spontaneously broken by topological charge transfer.