Magnetic raman scattering in two-dimensional spin-1/2 Heisenberg antiferromagnets: Spectral shape anomaly and magnetostrictive effects.

We calculate the Raman spectrum of the two-dimensional (2D) spin-1/2 Heisenberg antiferromagnet by exact diagonalization and quantum Monte Carlo techniques on clusters of up to 144 sites and, on a 16-site cluster, by considering the phonon-magnon interaction which leads to random fluctuations of the exchange integral. Results are in good agreement with experiments on various high-Tc precursors, such as La2CuO4 and YBa2Cu3O6.2. In particular, our calculations reproduce the broad lineshape of the two-magnon peak, the asymmetry about its maximum, the existence of spectral weight at high energies, and the observation of nominally forbidden A1g scattering. PACS numbers: 78.30.Hv, 75.50.Ee, 74.72.Jt Typeset using REVTEX