High Resolution Study of Spin Excitations in the Shastry-Sutherland   Singlet Ground State of SrCu2(BO3)2
  High resolution, inelastic neutron scattering measurements on SrCu2(BO3)2 reveal the dispersion of the three single triplet excitations continuously across the (H,0) direction within its tetragonal basal plane. These measurements also show distinct Q dependencies for the single and multiple triplet excitations, and that these excitations are largely dispersionless perpendicular to this plane. The temperature dependence of the intensities of these excitations is well described as the complement of the dc-susceptibility of SrCu2(BO3)2. 
B.D. Gaulin, S.H. Lee, S. Haravifard, J.P. Castellan, A.J. Berlinsky,   H.A. Dabkowska, Y. Qiu, J.R.D. Copley