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Spin ice is an experimental realization of a system with a topologically constrained phase at low temperature. The ice rules impose a divergence free condition leading to emergent dipolar correlations, extensive ground state entropy and non local zero energy excitations. An external field h lifts this degeneracy, leading to a perfectly ordered state via a Kasteleyn phase transition [1]. While this phenomenon is interesting by itself, a deeper study shows that the addition of another parameter such as a bond distortion makes this transition tunable and becomes, in the limit where h tends to zero, multicritical of infinite order, with a completely flat free energy function for all order parameter values. This poster will be illustrated by both analytic and numerical results.
[1] L. Jaubert, J.T. Chalker, P.C.W. Holdsworth and R. Moessner, Phys. Rev. Lett. 100, 067207 (2008). A long version of this paper is in preparation. |
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