Group theoretical classification of broken symmetry states of the two-folddegenerate Hubbard model on a triangular lattice

By a group theoretical procedure we derive the possible spontaneously broke n-symmetry states for the two-fold degenerate Hubbard model on a two-dimens ional triangular lattice. For ordering wave vectors corresponding to the po ints Gamma and K in the first BZ we find 22 states which include 16 colline ar and six non-collinear states. The collinear states include the usual SDW and CDW states which appear also in the single-band Hubbard model. The non -collinear states include exotic ordering states of orbitals and spins as w ell as the triangular arrangement of spins. (C) 2001 Elsevier Science B.V. All rights reserved.