Schedule Nov 15, 2007
Dimer Phases in Quantum Antiferromagnets with Orbital Degeneracy
George Jackeli, MPI & KITP

We study and solve the ground-state problem of a microscopic model for a family of orbitally degenerate quantum magnets. The orbital degrees of freedom are assumed to have directional character and are represented by static Potts-like variables. In the limit of vanishing Hund's coupling, the ground-state manifold of such a model is spanned by the hard-core dimer (spin singlet) coverings of the lattice. The extensive degeneracy of dimer coverings is lifted at a finite Hund's coupling through an order-out-of-disorder mechanism by virtual triplet excitations. The relevance of our results to several experimentally studied systems is discussed.

  1. G. Jackeli and D. Ivanov, Dimer phases in quantum antiferromagnets with orbital degeneracy, Phys. Rev. B 76, 132407 (2007)
  2. S. Di Matteo et al., Valence-bond crystal and lattice distortions in a pyrochlore antiferromagnet with orbital degeneracy, Phys. Rev. B 72, 024431 (2005)
  3. S. Di Matteo et al., Valence-Bond Crystal in a Pyrochlore Antiferromagnet with Orbital Degeneracy, Phys. Rev. Lett. 93, 077208 (2004)

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