A theory of Raman scattering in quasi-two-dimensional crystals is presented, emphasizing resonance enhancement at the excitonic transition appropriate to the ${\mathit{M}}_0$ and ${\mathit{M}}_1$ edges. The effect of electron-hole Coulomb interaction leads to metamorphism of the critical points. Our experimental results on quasi-two-dimensional InSe crystal show double resonant structure for both incident- and scattered-photon energies near the direct exciton energy. The theory provides a good fit to the experiments both above and below the excitonic transition after inclusion of the electron-hole interaction.

• Received 1 April 1991

DOI:https://doi.org/10.1103/PhysRevB.44.11133