Perturbation theory for magnetization plateaus and two triplet-dimer excitations in the 2D Shastry–Sutherland model

Abstract Magnetization process and two-triplet-dimer (TD) excitations in the Shastry–Sutherland model (SSM) are studied by using the perturbation expansion. Stability of the 1 3 plateau against the TD hopping is shown,and effects of the fourth-order two-body repulsion between TDs are discussed. We present the fifth-order results of the two-TD excitation spectra which show quite unique behavior due to the localized nature of a TD in the sea of singlet-dimers (SD).