Raman spectrum in thet-Jmodel

We have studied, using exact diagonalization techniques, the Raman spectrum in the t-J model in the zero- and one-hole subspace. In both sectors we obtain a very good agreement with experimental measurements in the ${\mathit{B}}_{1\mathit{g}}$ geometry. In the doped case the spectrum becomes broader, it is shifted to lower frequencies, and the peak at ≊2.97J, identified as a two-magnon process, disappears. We found that the low-energy excitations are string states and two-magnon processes in the neighborhood of the hole.