title: Spontaneous plaquette formation in the SU(4) spin-orbital ladder.
abstract: The low-energy properties of the SU(4) spin-orbital model on a two-leg ladder are studied by a variety of analytical and numerical techniques. As in the case of SU(2) models, there is a singlet-multiplet gap in the spectrum, but the ground state is twofold degenerate. An interpretation in terms of SU(4)-singlet plaquettes is proposed. The implications for general two-dimensional lattices are outlined.
authors.affiliation: Laboratoire de Physique Quantique, Université Paul Sabatier, 31062 Toulouse Cedex 04, France.
authors.forename: M
authors.initials: M
authors.lastname: van den Bossche
authors.forename: P
authors.initials: P
authors.lastname: Azaria
authors.forename: P
authors.initials: P
authors.lastname: Lecheminant
authors.forename: F
authors.initials: F
authors.lastname: Mila