title: Orbital ordering in e(g) orbital systems: ground states and thermodynamics of the 120° model.
abstract: Orbital degrees of freedom shape many of the properties of a wide class of Mott insulating, transition metal oxides with partially filled 3d shells. Here we study orbital ordering transitions in systems where a single electron occupies the e(g) orbital doublet and the spatially highly anisotropic orbital interactions can be captured by an orbital-only model, often called the 120° model. Our analysis of both the classical and quantum limits of this model in an extended parameter space shows that the 120° model is in close proximity to several T=0 phase transitions and various competing ordered phases. We characterize the orbital order of these nearby phases and their associated thermal phase transitions by extensive numerical simulations and perturbative arguments.
authors.affiliation: Physics Department, University of California, Santa Barbara, California 93106, USA.
authors.forename: Andre
authors.initials: A
authors.lastname: van Rynbach
authors.forename: Synge
authors.initials: S
authors.lastname: Todo
authors.forename: Simon
authors.initials: S
authors.lastname: Trebst