Spin dynamics of the spin dimer system TlCuCl3 probed by Raman spectroscopy -: art. no. 174412

Phonon and magnetic excitations in the strongly coupled spin dimer system TlCuCl3 have been studied by inelastic light scattering. We report the observation of a broadened two-magnon continuum with an unusual temperature dependence: upon cooling the spin gap is reduced and the peak energy of the continuum shifts to lower energy. This is attributed to dynamic spin-phonon interaction which leads to a phonon-modulated spin gap and exchange coupling constant. In addition, due to the large bandwidth and small spin gap of TlCuCl3, the interaction of thermally induced triplets is taken into account. Our results suggest the significance of spin-phonon coupling and thermally induced triplets to understand the collective spin dynamics of TlCuCl3.