The spin-SHeisenberg antiferromagnet on the Shastry-Sutherland lattice.

Recent advances in the orthogonal-dimer spin-Heisenberg antiferromagnet are reviewed. This model has been examined for more than 40 years since it was originally studied by Shastry and Sutherland. The discovery of SrCu(BO)as a good candidate material for thesystem led to a considerable advancement in subsequent research. In the case whenis larger than 1/2, however, the elucidation of the properties of the system was relatively delayed. In the ground state of general-systems, interesting quantum phase transitions occur not only for. In this article, the systematic behavior depending onwhich has been recently clarified by unbiased and numerical computational calculations is reviewed. The effects due to spin anisotropy as determined from experimental and theoretical results are also overviewed. We also mention recent developments for thesystem.