Excitonic order at strong-coupling : pseudo-spins , doping , and ferromagnetism

  title={Excitonic order at strong-coupling : pseudo-spins , doping , and ferromagnetism},
  author={Leon M. Balents},
A tight binding model is introduced to describe the strong interaction limit of excitonic ordering. At stoichiometry, the model reduces in the strong coupling limit to a pseudo-spin model with approximate U(4) symmetry. Excitonic order appears in the pseudospin model as in-plane pseudo-magnetism. The U(4) symmetry unifies all possible singlet and triplet order parameters describing such states. Super-exchange, Hunds-rule coupling, and other perturbations act as anisotropies splitting the U(4… CONTINUE READING