Spin excitations near the pressure-induced antiferromagnetic transition in SrCu2(BO3)2

SrCu2(BO3)2 is a frustrated quantum magnet which realizes the Shastry–Sutherland model. The system exhibits a sequence of pressure-induced phases, including a long-range antiferromagnetically ordered state. We have performed inelastic neutron scattering experiments on a single crystal at 4.2 (2) GPa, in the antiferromagnetic phase. The observed dispersive spin excitations were modeled using linear-spin-wave theory to extract exchange parameters. Our results are consistent with previously reported parameters at higher pressures and confirm the existence of a Goldstone mode as well as underlining the importance of the interlayer coupling. These results complement previous high-pressure studies and provide further input for theoretical models of SrCu2(BO3)2 under extreme conditions.