Frustrated spin-1/2 model in two dimensions with a known ground state

Abstract

A frustrated spin-1/2 model is constructed on the square lattice, the Hamiltonian of which contains five types of interactions: nearest-neighbor (NN), diagonal (D), next-nearest-neighbor (NNN), knight’s-move-distance away (KM), and further-neighbor diagonal (FND). The NN bonds in a particular direction, horizontal or vertical, are of alternating coupling strengths 7J and J. The other interaction strengths are: J (for NN and D), (J), J/2 (for NNN and KM), and J/4 (for FND). We prove that the exact ground state of the Hamiltonian is the columnar-dimer state.