Frustrated Orbital Exchange Models in p-band Mott Insulators

ORAL

Abstract

We investigate the general structure of orbital exchange physics in Mott-insulating states of p-orbital systems. Orbital orders occur in both the triangular and kagome lattices. In contrast, orbital exchange in the honeycomb lattice is frustrated as described by a novel quantum 120$^{\circ}$ model. Its classical ground states are mapped into configurations of the fully packed loop model with an extra U(1) rotation degree of freedom. Quantum orbital fluctuations select a six-site plaquette ground state ordering pattern in the semiclassical limit from the ``order from disorder'' mechanism. This effect arises from the appearance of a zero energy flat band of orbital excitations.

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Authors

  • Congjun Wu

    Department of Physics, University of California, San Diego, Department of Physics, University of California, San Diego, California 92093, University of California, San Diego, Department of Physics, University of California, San Diego, CA 92093