Theory of Charge and Orbital Ordering in the One-Dimensional Triangular-Lattice Vanadate BixV8O16

Abstract

We consider possible mechanism of the observed metal–insulator transition of a new vanadate material Bi x V 8 O 16 , which may be regarded as a one-dimensional, mixed valent version of the well-known triangular-lattice spin system LiVO 2 . Assuming the presence of strong inter-site Coulomb repulsion, which leads to the charge ordering of V 3+ and V 4+ ions, we derive an effective spin–orbit Hamiltonian by the strong-coupling perturbation theory, and by using the Lanczos diagonalization technique on small clusters, we obtain the orbital ordering patterns of the ground state in the parameter space. We find that a variety of phases appear as the ground state; we discuss their possible experimental relevance.