An Ising spin system which is situated on a two-dimensional square or a three-dimensional simple cubic lattice is considered. If there is a spin-lattice coupling and the lattice has no translational symmetry, there appears effectively a long range four-spin interaction in which the four spins are on a same axis. The ground state of the spin system is represented by using the ground state of a one-dimensional system where only the interactions along one axis are considered. The devil's staircase which has recently been shown to exist in such a one-dimensional system is wholly reproduced in a system on a two-dimensional square or a three-dimensional simple cubic lattice.
Abstract. Quantum spin-lattice systems in low dimensions exhibit a variety of interesting zero-temperature phases, some of which show non-classical (i.e., non-magnetic) long-range orders, such as dimer or trimer valence-bond order. These symmetry-breaking systems with localized valence bonds are referred to as valence-bond lattices (VBL) in this article. A review of our systematic microscopic formalism based on a proper set of composite operators for the ground and excited states of the VBL systems is given. The onedimensional (1D) spin-1 2 frustrated model is investigated in detail. Several possible VBL systems on the 1D spin-1 chains, the 2D square and kagomé lattices are also discussed. That our microscopic theory guarantees the rotational symmetry of the VBL systems is emphasized. 1.
Quantum spin-lattice systems in low dimensions exhibit a variety of interesting zero-temperature phases, some of which show non-classical (i.e., non-magnetic) long-range orders, such as dimer or trimer valence-bond order. These symmetry-breaking systems with localized valence bonds are referred to as valence-bond lattices (VBL) in this article. A review of our systematic microscopic formalism based on a proper set of composite operators for the ground and excited states of the VBL systems is given. The one-dimensional (1D) spin-
21 frustrated model is investigated in detail. Several possible VBL systems on the 1D spin-1 chains, the 2D square and {\it kagomé} lattices are also discussed. That our microscopic theory guarantees the rotational symmetry of the VBL systems is emphasized.