Spin nematic phase of the ferromagnetic dimer system on the Shastry-Sutherland lattice

The magnetization process of the S = 1/2 two-dimensional magnet where ferromagnetic dimers connected by the antiferromagnetic bond on the Shastry-Sutherland lattice is investigated using the numerical diagonalization of a finite-size cluster. We introduce the easy-axis anisotropy at the intradimer ferromagnetic interaction and consider the external magnetic field along the easy axis. It is found that the two-magnon bound state appears at higher magnetization regions for sufficiently large anisotropy. Base on the previous studies of several one-dimensional systems and the present calculation of the spin correlation function, the spin nematic order perpendicular to the external field is expected to occur in this two-magnon bound phase.