Exact two-spinon contribution to the longitudinal dynamical structure factor of the anisotropic XXZ model with comparison to DMRG simulations*

Motivated by inelastic neutron scattering experiments on quasi-one dimensional XXZ systems such as Yb₂Pt₂Pb, an exact formula for the two-spinon contribution to the dynamical structure factor is developed based on the quantum group (QG) approach. The results provide a QG derivation of the Baxter formula for the T=0 ordered spin. They are consistent with sum rules, and in excellent agreement with Density Matrix Renormalization Group (DMRG) simulations.