Quantum phase transitions of the S=1 Shastry-Sutherland model
  We investigate quantum phase transitions of the two-dimensional S=1 Shastry-Sutherland model, which is characterized by the frustrated orthogonal-dimer structure, by means of the exact diagonalization method and the Ising-type series expansion method. We clarify how distinct spin gap phases realized in the chain system are adiabatically connected to those in the two-dimensional Shastry-Sutherland model. The effect of single-ion anisotropy is also discussed. 
Akihisa Koga, Norio Kawakami and Manfred Sigrist