Mixed spin ladders with exotic ground states
arXiv:cond-mat/9712022 · doi:10.1007/s100510050475
Abstract
We study the "mixed spin" isotropic ladder system having S=1 spins on one leg and S=1/2 spins on the other, with general-type exchange interactions between spins on neighboring rungs. A set of model Hamiltonians with exact ground states in the form of a certain matrix product wave function is obtained. We show that sufficiently strong frustration can lead to exotic singlet ground states with infinite (exponential) degeneracy. We also list a couple of rather simple models with nontrivial ground states, including a model with only bilinear exchange.
8 pages, 2 figures, RevTeX, uses psfig.sty