Gia-Wei Chern, Muir J. Morrison, Cristiano Nisoli
The constraints of a realistic magnetic interaction limit the possibility of realizing degenerate vertex models with artificial spin ice in two dimensions. Here we present and study a novel vertex-frustrated geometry which exhibits a residual entropy density. While interesting in its own regard as a new form of frustration in a vertex system, our lattice opens new pathways for implementing degeneracy in artificial magnetic nanoarrays, a task so far elusive. We demonstrate that its degenerate ground state can be mapped to the disordered phase of the exactly solvable F-model. Monte Carlo simulations extend our study to thermal states, and, significantly, find algebraic correlations for frustrated vertices, magnetic charges, and spins in the ground state, pointing to a critical phase.
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http://arxiv.org/abs/1210.8377
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