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Zn-Paratacamite is a rare spin 1/2 antiferromagnetic insulator with an ideal kagome lattice structure in part of its phase diagram. As a function of Zn doping, this material undergoes a structural distortion which relieves the frustration and introduces magnetic order in the ground state, though the precise nature of the order is not clear at this point. In this paper, we present evidence for N\'eel ordering in the {\it strongly} distorted phase of Zn-Paratacamite through the application of quantum Monte-Carlo techniques. These numerical results strongly support a recent Schwinger-boson mean field theory of Zn-Paratacamite. For weak distortion, using exact diagonalization to study small clusters, our results indicate a large basin of stability of the ideal kagome lattice ground state in the presence of distortion of this type and that the ground state in this regime wants to break a glide-plane symmetry. This symmetry breaking in the undistorted limit lends strong support to recent valence bond solid ground state proposals. Thus the phase transition between the two phases may be in the deconfined universality class or first order. |
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