Multiple singlet and triplet states in the 2D orthogonal-dimer compound SrCu2(BO3)2

Abstract The compound SrCu 2 (BO 3 ) 2 is a quantum spin system with a 2D arrangement of orthogonal spin dimers, an exact singlet ground state and a singlet–triplet gap Δ 01 =34 K. Triplet excitations in this compound are extremely localized and strongly interacting due to the strong inherent frustration. Experimentally, two triplet modes were observed both in neutron scattering and ESR investigations. In Raman scattering experiments further well-defined modes with energies close to Δ 01 exist for low temperatures ( T ⪡ Δ 01 ). The properties of these modes resemble the magnetic bound states found in dimerized spin chain and spin ladder systems.