Semiclassical ordering in the large-N pyrochlore antiferromagnet.
We study the semiclassical limit of the Sp(N) generalization of the pyrochlore lattice Heisenberg antiferromagnet by expanding about the N --> infinity saddlepoint in powers of a generalized inverse spin. To leading order, we write down an effective Hamiltonian as a series in loops on the lattice. Using this as a formula for calculating the energy of any classical ground state, we perform Monte Carlo simulations and find a unique collinear ground state. This state is not a ground state of linear spin-wave theory, and can therefore not be a physical (N = 1) semiclassical ground state.
Hizi
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U
Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853-2501, USA. uh22@cornell.edu
Sharma
Prashant
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Henley
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CL