We experimentally study the behavior of geometrically frustrated quasi-two-dimensional colloidal crystals with both attractive and repulsive interparticle interactions. We create a two-dimensional triangular lattice by confining a monolayer of close-packed micron-sized spheres between two parallel glass coverslips. The wall separation is slightly larger than one particle diameter, which facilitates buckling in the monolayer of particles. Each particle can occupy either a buckled up or down position on its lattice site, where neighboring particles favor opposite positions to maximize their free volume and hence frustrates the third neighbor. Thus, our system is analogous to the Ising antiferromagnet on a triangular lattice where particle up-down position is analogous to Ising spins. Using video microscopy, we measure the temporal evolution of each spin" and tune the "Ising coupling constant" by adjusting the interparticle interaction. Our preliminary results show the transition of this coupling constant from antiferromagnetic to ferromagnetic in our system.<br/><br/>

Antiferromagnetic to ferromagnetic transition in geometrically frustrated quasi-two-dimensional colloidal crystals

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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