Flux expulsion and greedy bosons: Frustrated magnets at large N

O. Tchernyshyov, R. Moessner, Shivaji Lal Sondhi

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42 Scopus citations


We investigate the Sp(N) mean-field theory for frustrated quantum magnets. First, we establish some general properties of its solutions; in particular, for small spin we propose simple rules for determining the saddle points of optimal energy. We then apply these insights to the pyrochlore lattice. For spins on a single tetrahedron, we demonstrate a continuous ground-state degeneracy for any value of the spin length. For the full pyrochlore lattice, this degeneracy translates to a large number of near-degenerate potential saddle points. Remarkably, it is impossible to construct a saddle point with the full symmetry of the Hamiltonian -at large N, the pyrochlore magnet cannot be a spin liquid. Nonetheless, for realistic finite values of N, tunnelling between the nearly degenerate saddle points could restore the full symmetry of the Hamiltonian.

Original languageEnglish (US)
Pages (from-to)278-284
Number of pages7
Issue number2
StatePublished - Jan 15 2006

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


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