Figure 1: The SrCu2(BO3)2 lattice.
(a) Heisenberg and DM couplings in SrCu2(BO3)2. The red and blue arrows on dimers represent the intra-dimer DM vectors D (black arrows indicate the order of spins in the DM term). The inter-dimer coupling D′ has in-plane and out-of-plane components. Following the circular arrows as indicated, the out-of-plane DM component points out of the plane (purple circles). The ‘staggered’ in-plane component is shown by magenta arrows. The green rectangle indicates the structural unit cell. (b) The new reduced unit cell upon taking the two dimers to be equivalent is shown in the yellow square. The dimers form a square lattice as shown.
