ORBITAL ORDERING IN A 2-DIMENSIONAL TRIANGULAR LATTICE

We discuss the role of orbital ordering in a two-dimensional triangula r lattice. Usually, this lattice is considered as ''frustrated.'' We s how that a peculiar type of orbital ordering can remove this frustrati on if we allow for orbital degeneracy. Wt: pay special attention to th e d(2) case, for which we present mean field calculations for possible orbital orderings and an exact diagonalization study of a three-site cluster within a degenerate Hubbard model. The results support the pos sibility of an orbitally ordered singlet ground state. In particular, it provides new insight to the magnetic phase transition and the low t emperature phase of LiVO2.