The ring-exchange (RE) interaction in a Mott insulator with doubly degenerate eg orbitals is studied. The Hamiltonian for the RE interaction is derived by a perturbational calculation. A remarkably weak RE interaction destroys the orbital order caused by the order-by-fluctuation mechanism in the nearest-neighbor exchange-interaction model. A magnetic octupole moment with long range order, i.e., complex orbital wave functions, appears. Competition between octupole and quadrupole interactions strongly suppresses the ordered moments.
|Journal||journal of the physical society of japan|
|Publication status||Published - 2011 Mar|
- Octupole order
- Orbital order
- Ring-exchange interaction
ASJC Scopus subject areas
- Physics and Astronomy(all)